Circuit board checker and circuit board checking method

ABSTRACT

The present invention provides an inspection apparatus for circuit board for conducting electrical inspection by electrically connecting inspection object electrodes of the circuit board to a plurality of inspection electrodes formed in accordance with a pattern corresponding to the inspection object electrodes through an anisotropically conductive sheet, wherein each of an upper-side board-compressing member and a lower-side board-compressing member respectively arranged on an upper side and lower side of the inspection object circuit board is provided on upper-side base plate and lower-side base plate supported by a plurality of supports of support-infixing plates, and an upper-side supporting point and a lower-side supporting point corresponds to the respective supports on the respective base plates are arranged at positions different from each other on a plane of projection in a thickness-wise direction of the upper-side board-compressing member and lower-side board-compressing member when the inspection apparatus is seen through from above, whereby being capable of conducting the inspection high in reliability even to the circuit board small in such as size of the inspection object electrodes, and an inspection process for circuit board.

TECHNICAL FIELD

The present invention relates to an inspection apparatus for circuitboard and an inspection process for circuit board.

BACKGROUND ART

In electrical inspection of a circuit board, it is conducted to measurean electric resistance between electrodes of an inspection objectcircuit board (hereinafter also referred to as “circuit board to beinspected”).

In the measurement of an electric resistance of a circuit board, therehas heretofore been adopted, for example, a means in which probes PA andPD for current supply and probes PB and PC for voltage measurement arepressed against and brought into respective contact with 2 inspectionobject electrodes 81 and 82 (hereinafter also referred to as “electrodesto be inspected”), which have been electrically connected to each otherin a circuit board 80 to be inspected, as illustrated in FIG. 15, acurrent is supplied between the proves PA and PD for current supply froma power supply device 83 in this state, and a voltage signal detected bythe probes PB and PC for voltage measurement at this time is processedin an electric signal processor 84, thereby determining an electricresistance value between the electrodes 81 and 82 to be inspected.

In the method described above, however, the surfaces of the electrodes81 and 82 to be inspected may be damaged by pressing the probes becauseit is necessary to bring the probes PA and PD for current supply and theprobes PB and PC for voltage measurement into respective contact withthe electrodes 81 and 82 to be inspected by considerably great pressingforce, the probes are made of a metal, and the tips thereof are pointed,so that the circuit board becomes unusable. Under such circumstances,the electric resistance measurement cannot be carried out on all circuitboards to be provided as products, and so the method cannot helpadopting the so-called sampling inspection, and after all, the yield ofthe products cannot be increased.

In order to solve such a problem, there have heretofore been proposedinspection apparatus in which a connecting member coming into contactwith electrodes to be inspected is formed by an anisotropicallyconductive sheet (see, for example, Prior Art. 1 to Prior Art. 3).

According to such inspection apparatus, an electrode for current supplyand an electrode for voltage measurement are brought into contact withelectrodes to be inspected of a circuit board to be inspected throughthe anisotropically conductive sheet, whereby electrical connection isachieved, so that the measurement of electric resistance can beconducted without damaging the electrodes to be inspected.

As a certain kind of inspection apparatus which achieves electricalconnection to electrodes to be inspected through an anisotropicallyconductive sheet, is used, for example, an apparatus of the constructionthat an upper-side board-compressing member 91A arranged on an uppersurface side of a circuit board 1 to be inspected, on which upper-sideelectrodes 2 to be inspected are provided, and having an anisotropicallyconductive sheet 93A on its front surface (lower surface in FIG. 16),and a lower-side board-compressing member 91B arranged on a lowersurface side of the circuit board 1 to be inspected, on which lower-sideelectrodes 3 to be inspected are provided, and having an anisotropicallyconductive sheet 93B on its front surface (upper surface in FIG. 16) arearranged so as to be opposed to each other in vertical direction asillustrated in FIG. 16.

In such an inspection apparatus (hereinafter also referred to as “firstconventional apparatus”) 90, the upper-side board-compressing member 91Aand lower-side board-compressing member 91B are respectively provided onbase plates 96A and 96B supported by a plurality of supports 94A and 94Brespectively infixed into flat plate-like support-infixing plates 95Aand 95B and vertically extending from the support-infixing plates 95Aand 95B, and as illustrated in FIG. 17, supporting points 97A formed bythe supports 94A on the base plate 96A and supporting points 97B formedby the supports 94B on the base plate 96B on a plane M4 of projection ina thickness-wise direction of the base plates 96A, 96B when the firstconventional apparatus 90 is seen through from above are located at thesame positions. In FIG. 17, the supporting points (hereinafter alsoreferred to as “upper-side supporting points”) 97A related to theupper-side board-compressing member 91A and the supporting points(hereinafter also referred to as “lower-side supporting point”) 97Brelated to the lower-side board-compressing member 91B are indicated bya black circle and a white circle, respectively.

In FIG. 16, reference numeral 92A designates a circuit board forinspection, on which electrodes for current supply and electrodes forvoltage measurement (both not illustrated) making up pairs of inspectionelectrodes corresponding to the upper-side electrodes 2 to be inspectedhave been formed, reference character 92B designates a circuit board forinspection, on which electrodes for current supply and electrodes forvoltage measurement (both not illustrated) making up pairs of inspectionelectrodes corresponding to the lower-side electrodes 3 to be inspectedhave been formed, reference numerals 98A and 98B designate electrodedevices electrically connected to the respective circuit boards 92A and92B for inspection and a tester (not illustrated), and referencenumerals 99A and 99B designate anisotropically conductive sheets.

In this first conventional apparatus 90, the support-infixing plates 95Aand 95B related to each of the upper-side board-compressing member 91Aand lower-side board-compressing member 91B are moved in directionsapproaching to the circuit board 1 to be inspected, thereby pressing thebase plates 96A and 96B by the supports 94A and 94B to compress thecircuit board 1 to be inspected by the upper-side board-compressingmember 91A and lower-side board-compressing member 91B. As a result, ameasurable state is brought about. In this measurable state, theanisotropically conductive sheets 93A and 93B provided on the respectivesurfaces of the upper-side board-compressing member 91A and lower-sideboard-compressing member 91B are brought into contact with pressure withthe respective electrodes to be inspected of the circuit board 1 to beinspected, whereby measurement of electric resistance is carried out byapplying pressure to the respective electrodes to be inspected.

With respect to a printed circuit board for generally mountingintegrated circuits or the like, it is necessary to confirm that awiring pattern of the circuit board has the expected performance beforethe integrated circuits or the like are mounted. Therefore, theinspection of the electrical properties thereof is conducted. As aninspection apparatus for inspecting such a circuit board, there is knownthat having the construction that anisotropically conductive sheet isintervened between an inspection object circuit board and a plurality ofinspection electrodes arranged in accordance with a patterncorresponding to inspection object electrodes of the inspection objectcircuit board to conduct the electrical inspection of the inspectionobject circuit board (see, for example, Prior Art. 4).

As a certain kind of inspection apparatus for such a circuit board, isused, for example, an apparatus having the construction that anupper-side board-compressing member 101A having a circuit board 102 forinspection, on which inspection electrodes 102A corresponding toupper-side electrodes 2 to be inspected of an inspection object circuitboard (circuit board to be inspected) 1 have been formed, and alower-side board-compressing member 101B having a circuit board 107 forinspection, on which inspection electrodes 107A corresponding tolower-side electrodes 3 to be inspected have been formed, which arearranged on an upper side having the upper-side electrodes 2 to beinspected and on a lower side having the lower-side electrodes 3 to beinspected in the circuit board 1 to be inspected, respectively, arearranged so as to be opposed to each other in vertical direction asillustrated in FIG. 18, and the upper-side board-compressing member 101Aand lower-side board-compressing member 101B are respectively providedon base plates 106 supported by a plurality of supports 104 infixed intoflat plate-like support-infixing plates 105 and vertically extendingfrom the support-infixing plates 105.

In this inspection apparatus (hereinafter also referred to as “secondconventional apparatus”) 100, anisotropically conductive sheets 103 areprovided on the respective surfaces of the circuit boards 102 and 107for inspection. In FIG. 18, reference numeral 108 designates electrodedevices electrically connected to the respective circuit boards 102 and107 for inspection and a circuit board for inspection of a tester (notillustrated), and reference numeral 109 designates anisotropicallyconductive sheet.

In this second conventional apparatus 100, the support-infixing plates105 related to each of the upper-side board-compressing member 101A andlower-side board-compressing member 101B are moved in directionsapproaching to the circuit board 1 to be inspected, thereby pressing thebase plates 106 by the supports 104 to compress the circuit board 1 tobe inspected by the upper-side board-compressing member 101A andlower-side board-compressing member 101B. As a result, a measurablestate is brought about.

In this second conventional apparatus 100, as with the firstconventional apparatus 90, upper-side supporting points formed by thesupports 104 on the base plate 106 related to the upper-sideboard-compressing member 101A and lower-side supporting points formed bythe supports 104 on the base plate 106 related to the lower-sideboard-compressing member 101B on a plane of projection in athickness-wise direction of the base plates when the second conventionalapparatus 100 is seen through from above are located at the samepositions.

In the conventional apparatus of the above-described construction, theanisotropically conductive sheet is a sheet exhibiting conductivity onlyin its thickness-wise direction or having pressure-sensitive conductiveconductor parts exhibiting conductivity only in the thickness-wisedirection when they are pressurized in the thickness-wise direction.Since the anisotropically conductive sheet has such features thatcompact electrical connection can be achieved without using any meanssuch as soldering or mechanical fitting, and that soft connection isfeasible with mechanical shock or strain absorbed therein, it functionsas a connector for achieving electrical connection making use of suchfeatures.

On the other hand, in recent years, the size and pitch or clearance ofelectrodes in a circuit board have tended to become small for thepurpose of achieving a high degree of integration.

In an inspection apparatus for inspecting such a circuit board, thathaving a small thickness is used as the anisotropically conductive sheetfor the purpose of exactly electrically connecting electrodes to beinspected of the circuit board to be inspected to inspection electrodescorresponding to the electrodes to be inspected. The anisotropicallyconductive sheet having the small thickness involves a problem that itcannot sufficiently absorb strain due to deflection caused to the baseplate by being pressed by the supports, and so, in the measurable state,a scatter of pressure distribution tends to occur on the circuit boardto be inspected to encounter difficulty in applying even pressure to therespective electrodes to be inspected of the circuit board to beinspected.

In the inspection apparatus having such a thin anisotropicallyconductive sheet, the inspection is conducted with great pressing forcefor applying pressure of at least a certain value to all the electrodesto be inspected of the circuit board to be inspected to achieve expectedmeasurable state as to the respective electrodes to be inspected of thecircuit board to be inspected, and so great pressure is also applied tothe anisotropically conductive sheet at every inspection. Therefore, theanisotropically conductive sheet is liable to be deteriorated. As aresult, a problem that inspection efficiency is lowered as theanisotropically conductive sheet is required to be frequently replacedin the inspection apparatus also arises.

In the inspection apparatus, it is thus investigated to make thethickness of the base plate greater for lessening the deflection of thebase plate caused by pressing of the supports.

However, when the thickness of the base plate making up the inspectionapparatus is made great, points of application of the pressing forceapplied to the circuit board to be inspected by the supports through thebase plates and board-compressing members are formed at the samepositions on a plane of projection in a thickness-wise direction of theboard-compressing members when the inspection apparatus is seen throughfrom above. The pressing force is thus concentrated on the points ofapplication in the circuit board to be inspected, and so the pressingforce at the points of application becomes greatest, and the pressingforce at positions distant from the points of application becomessmaller as the distance from the points of application is greater. Ascatter of pressure distribution is thus caused. As a result, a problemthat a scatter of electrically connected state related to the electrodesto be inspected of the circuit board to be inspected is caused isinvolved. Another problem that the weight of the apparatus itself isincreased by the increase in the thickness of the base plate is alsoinvolved.

When the thickness of base plates is made great in an inspectionapparatus having the construction that through-holes are formed in thebase plates, a problem that the step of forming the through-holes in thebase plates becomes complicated in the production process thereof tolower productivity is also involved.

More specifically, when it is intended to form a through-hole in a thickbase plate by one drilling operation, for example, a drill bit is liableto be damaged or broken. Therefore, the through-hole is generally formedby means of a method in which a concave hole is formed by conducting adrilling operation from one side of the base plate, and a drillingoperation is also conducted from the other side of the base plate toform a concave hole so as to be linked to the first-mentioned concavehole. Since one through-hole is formed in such a manner, it is necessaryto conduct the drilling operation plural times. It thus takes a longtime to conduct the drilling operations, and moreover there is apossibility that the concave holes formed by the respective drillingoperations may not be linked in an expected state, so that thethrough-holes cannot be formed with high efficiency.

Prior Art. 1: Japanese Patent Application Laid-Open No. 26446/1997;

Prior Art. 2: Japanese Patent Application Laid-Open No. 2000-74965;

Prior Art. 3: Japanese Patent Application Laid-Open No. 2000-241485;

Prior Art. 4: Japanese Patent Application Laid-Open No. 183974/1991.

DISCLOSURE OF THE INVENTION

The present invention has been made on the basis of the foregoingcircumstances and has as its first object the provision of alight-weight inspection apparatus for circuit board capable ofconducting electrical inspection of a circuit board with highreliability even when the inspection object circuit board has inspectionobject electrodes small in size and pitch or clearance.

A second object of the present invention is to provide an inspectionprocess for circuit board capable of conducting electrical inspection ofa circuit board with high reliability even when the circuit board hasinspection object electrodes small in size and pitch or clearance.

A third object of the present invention is to provide a light-weightinspection apparatus for circuit board capable of conducting electricalinspection of a circuit board with high reliability even when thecircuit board has inspection object electrodes small in size and pitchor clearance, capable of easily designing miniaturization andsimplification, and capable of being produced at low cost and capable ofinhibit the deterioration of an anisotropically conductive sheet uponinspection.

A fourth object of the present invention is to provide a light-weightinspection apparatus for circuit board having a structure that achieveshigh productivity and capable of conducting electrical inspection of acircuit board with high reliability even when the circuit board hasinspection object electrodes small in size and pitch or clearance.

According to the present invention, there is thus provided an inspectionapparatus for circuit board for conducting electrical inspection of aninspection object circuit board by electrically connecting inspectionobject electrodes of the inspection object circuit board to a pluralityof inspection electrodes formed in accordance with a patterncorresponding to the inspection object electrodes through ananisotropically conductive sheet, which comprises

an upper-side board-compressing member arranged on an upper side of theinspection object circuit board and a lower-side board-compressingmember arranged on a lower side of the inspection object circuit board,

wherein either one of the upper-side board-compressing member andlower-side board-compressing member has the plurality of the inspectionelectrodes, the upper-side board-compressing member and lower-sideboard-compressing member are respectively provided on base platessupported by a plurality of supports infixed into support-infixingplates, and an upper-side supporting point corresponds to the upper-sidesupport on the upper-side base plate related to the upper-sideboard-compressing member and a lower-side supporting point correspondsto the lower-side support on the lower-side base plate related to thelower-side board-compressing member are arranged at positions differentfrom each other on a plane of projection in a thickness-wise directionof the upper-side board-compressing member and lower-sideboard-compressing member when the inspection apparatus is seen throughfrom above.

In the inspection apparatus for circuit board according to the presentinvention, it may be preferable that the upper-side board-compressingmember has an anisotropically conductive sheet on its surface, and thelower-side board-compressing member has an anisotropically conductivesheet on its surface.

In the inspection apparatus for circuit board according to the presentinvention, the upper-side base plate and the lower-side base plate ispressed, respectively, by the upper-side supports and the lower-sidesupports, thereby bringing about a measurable state that the inspectionobject circuit board is compressed by the upper-side board-compressingmember and lower-side board-compressing member.

In the inspection apparatus for circuit board according to the presentinvention, in the measurable state, a complex stack composed of theinspection object circuit board and the upper-side board-compressingmember and lower-side board-compressing member for compressing theinspection object circuit board is deformed by shifting in thethickness-wise direction together with the upper-side base plate andlower-side base plate, at positions, over the whole body, respectivelypressed by the upper-side supports and lower-side supports in accordancewith the upper-side supporting points and lower-side supporting points.

In the measurable state, a gap in the thickness-wise direction of thecomplex stack between a tip level in the upper-side support and a tiplevel in the lower-side support may be smaller than the total thicknessof the complex stack, the upper-side base plate and the lower-side baseplate.

In the inspection apparatus for circuit board according to the presentinvention, it may be preferable that the upper-side supporting pointsand the lower-side supporting points be formed in the form of a latticeon the upper-side base plate and on the lower-side base plate,respectively, and

on the plane of projection in the thickness-wise direction of theupper-side board-compressing member and the lower-side board-compressingmember, only one lower-side supporting point be arranged within anupper-side unit region partitioned by adjacent 4 upper-side supportingpoints, and only one upper-side supporting point be arranged within alower-side unit region partitioned by adjacent 4 lower-side supportingpoints.

In the inspection apparatus for circuit board, clearances betweenupper-side supporting points adjacent to each other related to theupper-side unit region, and between lower-side supporting pointsadjacent to each other related to the lower-side unit region maypreferably be each 10 to 100 mm.

In the inspection apparatus for circuit board according to the presentinvention, the upper-side base plate and lower-side base plate maypreferably be each composed of an insulating material having aresistivity of at least 1×10¹⁰ Ω·cm, and have a thickness of 1 to 10 mm.

In inspection apparatus for circuit board according to the presentinvention, the thickness of each of the upper-side base plate andlower-side base plate may preferably be at most 5 mm.

According to the present invention, there is also provided an inspectionprocess for circuit board, which comprises

using the inspection apparatus for circuit board described above,

pressing the upper-side base plate and the lower-side base plate by theupper-side supports and the lower-side supports, respectively, to form ameasurable state that an inspection object circuit board is compressedby the upper-side board-compressing member and lower-sideboard-compressing member, and

in this measurable state, deforming a complex stack composed of theinspection object circuit board and the upper-side board-compressingmember and lower-side board-compressing member for compressing theinspection object circuit board by shifting in the thickness-wisedirection together with the upper-side base plate and lower-side baseplate, at positions, over the whole body, respectively pressed by theupper-side supports and lower-side supports in accordance with theupper-side supporting points and lower-side supporting points.

According to the present invention, there is further provided aninspection apparatus for circuit board for measuring an electricresistance of an inspection object circuit board by electricallyconnecting a pair of inspection electrodes formed of an electrode forcurrent supply and an electrode for voltage measurement arranged inrelation separated from each other to each of a plurality of inspectionobject electrodes formed on the inspection object circuit board, throughan anisotropically conductive sheet, which comprises

an upper-side board-compressing member arranged on an upper side of theinspection object circuit board and having an anisotropically conductivesheet on its surface, and a lower-side board-compressing member arrangedon a lower side of the inspection object circuit board and having ananisotropically conductive sheet on its surface,

wherein the upper-side board-compressing member and lower-sideboard-compressing member each have plural pairs of inspection electrodesand are respectively provided on base plates supported by a plurality ofsupports infixed into support-infixing plates, and an upper-sidesupporting point corresponds to the upper-side support on the upper-sidebase plate related to the upper-side board-compressing member and alower-side supporting point corresponds to the lower-side support on thelower-side base plate related to the lower-side board-compressing memberare arranged at positions different from each other on a plane ofprojection in a thickness-wise direction of the upper-sideboard-compressing member and lower-side board-compressing member whenthe inspection apparatus is seen through from above.

In the inspection apparatus for circuit board according to the presentinvention, the upper-side base plate and the lower-side base plate ispressed, respectively, by the upper-side supports and the lower-sidesupports, thereby bringing about a measurable state that the inspectionobject circuit board is compressed by the upper-side board-compressingmember and lower-side board-compressing member to carry out themeasurement of the electric resistance.

In the inspection apparatus for circuit board according to the presentinvention, in the measurable state, a complex stack composed of theinspection object circuit board, and the upper-side board-compressingmember and lower-side board-compressing member for compressing theinspection object circuit board is deformed by shifting in thethickness-wise direction together with the upper-side base plate andlower-side base plate, at positions, over the whole body, respectivelypressed by the upper-side supports and lower-side supports in accordancewith the upper-side supporting points and lower-side supporting points.

In the inspection apparatus for circuit board according to the presentinvention, in the measurable state, a gap in the thickness-wisedirection of the complex stack between a tip level in the upper-sidesupport and a tip level in the lower-side support may be smaller thanthe total thickness of the complex stack, the upper-side base plate andthe lower-side base plate.

In inspection apparatus for circuit board according to the presentinvention, the thickness of each of the upper-side base plate andlower-side base plate may preferably be at most 5 mm.

In the inspection apparatus for circuit board according to the presentinvention, it may be preferable that the upper-side supporting pointsand the lower-side supporting points be formed in the form of a latticeon the upper-side base plate and on the lower-side base plate,respectively, and

on the plane of projection in the thickness-wise direction of theupper-side board-compressing member and the lower-side board-compressingmember, only one lower-side supporting point be arranged within anupper-side unit region partitioned by adjacent 4 upper-side supportingpoints, and only one upper-side supporting point be arranged within alower-side unit region partitioned by adjacent 4 lower-side supportingpoints.

In the inspection apparatus for circuit board according to the presentinvention, clearances between upper-side supporting points adjacent toeach other related to the upper-side unit region, and between lower-sidesupporting points adjacent to each other related to the lower-side unitregion may preferably be each 10 to 100 mm.

In inspection apparatus for circuit board according to the presentinvention, the upper-side base plate and lower-side base plate maypreferably be each composed of a glass fiber-reinforced epoxy resin andhave a thickness of 2 to 5 mm.

According to the present invention, there is still further provided aninspection process for circuit board, which comprises

using the inspection apparatus for circuit board described above, and

in a measurable state that an inspection object circuit board iscompressed by the upper-side board-compressing member and lower-sideboard-compressing member by pressing the upper-side base plate and thelower-side base plate by the upper-side supports and the lower-sidesupports, respectively, deforming a complex stack composed of theinspection object circuit board and the upper-side board-compressingmember and lower-side board-compressing member for compressing theinspection object circuit board by shifting in the thickness-wisedirection together with the upper-side base plate and lower-side baseplate, at positions, over the whole body, respectively pressed by theupper-side supports and lower-side supports in accordance with theupper-side supporting points and lower-side supporting points, so as tocarry out measurement of electric resistance.

EFFECTS OF THE INVENTION

According to the inspection apparatus for circuit board of the presentinvention, points of application of the pressing force by the upper-sidesupports and points of application of the pressing force by thelower-side supports are formed at positions different from one anotheron the plane of projection in the thickness-wise direction of theupper-side board-compressing member and lower-side board-compressingmember in the measurable state, and the complex stack, in which theinspection object circuit board is compressed, is, as it were, forcedlydeformed together with the base plates in accordance with the upper-sidesupporting points and lower-side supporting points forming the points ofapplication, thereby inhibiting the pressing force from concentrating onthe points of application. As a result, since the pressure distributionin the inspection object circuit board is uniformed, a state that allthe inspection object electrodes in the inspection object circuit boardhave been evenly electrically connected to inspection electrodescorresponding to each of the inspection object electrodes can beattained, so that the electrical inspection of the circuit board can beconducted with high accuracy.

Since both upper-side base plate and lower-side base plate arepreferably made thinner for the purpose of achieving such a state, theweight of the whole inspection apparatus is made light by the reductionof the mass of the upper-side base plate and lower-side base plate.

Accordingly, according to the inspection apparatus for circuit board ofthe present invention, the thickness of the anisotropically conductivesheets can be made thin without involving defectiveness, so that theelectrical inspection of a circuit board can be conducted with highreliability even when the circuit board has inspection object electrodessmall in size and pitch or clearance, and moreover the weight saving ofthe measuring apparatus itself can be expected.

According to the inspection apparatus for circuit board of the presentinvention, the conduction between each of the inspection objectelectrodes in the inspection object circuit board and inspectionelectrode can be achieved with small pressing force to bring about themeasurable state, so that durable strength in pressurization required ofcomponent members of the inspection apparatus may be made low. As aresult, members relatively low in durable strength in pressurization canbe used as the component members without involving defectiveness,whereby the miniaturization and simplification of the inspectionapparatus itself can be planed, and reduction of cost can be expected.

Since the electrical inspection of the inspection object circuit boardcan be conducted with small pressing force, the deterioration of theanisotropically conductive sheets caused by repeated pressurization atevery inspection can be inhibited. Accordingly, the frequency ofreplacement of the anisotropically conductive sheets in the inspectionapparatus can be lessened, so that high inspection efficiency can beachieved, and inspection cost can be reduced.

Further, since thin base plates may preferably be used in the inspectionapparatus for circuit board according to the present invention, evenwhen the inspection apparatus has the construction that through-holesare formed in the base plates, the time required for the drillingoperation can be shortened compared with an inspection apparatusequipped with thick base plates and the through-holes can be formed withhigh efficiency to attain high productivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the construction of an exemplary inspection apparatusfor circuit board according to the present invention together with aninspection object circuit board.

FIG. 2 is a cross-sectional view illustrating, on an enlarged scale, apart of the inspection apparatus for circuit board shown in FIG. 1.

FIG. 3 illustrates the degree of flexibility required of an inspectionobject circuit board.

FIG. 4 illustrates a positional relation between upper-side supportingpoints and lower-side supporting points on a plane of projection in athickness-wise direction of an upper-side board-compressing member and alower-side board-compressing member when the inspection apparatus forcircuit board shown in FIG. 1 is seen through from above.

FIG. 5 illustrates an upper-side adaptor in the upper-sideboard-compressing member making up the inspection apparatus for circuitboard shown in FIG. 1 together with an upper-side inspection head andthe inspection object circuit board.

FIG. 6 illustrates a front surface of a circuit board for inspection inthe inspection apparatus for circuit board shown in FIG. 1.

FIG. 7 illustrates a back surface of the circuit board for inspection inthe inspection apparatus for circuit board shown in FIG. 1.

FIG. 8 is a cross-sectional view taken along line X-X′ of the circuitboard for inspection shown in FIGS. 6 and 7.

FIG. 9 is a cross-sectional view illustrating an inspection pin makingup the upper-side board-compressing member of the inspection apparatusfor circuit board shown in FIG. 1.

FIG. 10(a) is a plan view illustrating a positional relation between aprojected part of a lower-side base plate and an alignment movableplate, and FIG. 10(b) is a cross-sectional view illustrating apositional relation between a projected part of a lower-side base plateand an alignment movable plate.

FIG. 11 is a cross-sectional view illustrating an inspection pin makingup the lower-side board-compressing member of the inspection apparatusfor circuit board shown in FIG. 1.

FIG. 12 illustrates a measurable state of the inspection apparatus forcircuit board shown in FIG. 1.

FIG. 13 is a cross-sectional view illustrating, on an enlarged scale, apart of the construction of another exemplary inspection apparatus forcircuit board according to the present invention.

FIG. 14 is a cross-sectional view illustrating the construction of afurther exemplary inspection apparatus for circuit board according tothe present invention.

FIG. 15 typically illustrates an apparatus for measuring electricresistance between electrodes in a circuit board by probes for currentsupply and probes for voltage measurement.

FIG. 16 illustrates the construction of an exemplary conventionalinspection apparatus for circuit board together with an inspectionobject circuit board.

FIG. 17 illustrates a positional relation among supporting points on aplane of projection when the inspection apparatus for circuit boardshown in FIG. 16 is seen through from above.

FIG. 18 illustrates the construction of another exemplary conventionalinspection apparatus for circuit board together with an inspectionobject circuit board.

DESCRIPTION OF CHARACTERS

-   1 Inspection object circuit board,-   2 Upper-side electrodes to be inspected,-   3 Lower-side electrodes to be inspected,-   10 Inspection apparatus,-   11 Inspection-executing region,-   13 Positioning pins,-   15 Alignment movable plate,-   15A Substantially rectangular hole,-   16 Alignment support,-   19 Complex stack,-   21 Upper-side base plate,-   21A Upper-side supporting points,-   21B Through-hole for inspection pin,-   22 Upper-side supports,-   22A Proximal part,-   22B Tip part,-   23 Upper-side support-infixing plate,-   25 Lower-side base plate,-   25A Projected part,-   25B Lower-side supporting points,-   25C Through-hole for positioning pin,-   25D Through-hole for inspection pin,-   26 Lower-side supports,-   26A Proximal part,-   26B Tip part,-   27 Lower-side support-infixing plate,-   30 Upper-side board-compressing member,-   31 Upper-side adaptor,-   32 Circuit board for inspection,-   32A Electrodes for current supply,-   32B Electrodes for voltage measurement,-   32C Terminal electrodes,-   32D Internal wiring part,-   32E Positioning holes,-   33 Anisotropically conductive sheet,-   35 Upper-side inspection head,-   36 Inspection pins,-   36A Tip part,-   36B Central part,-   36C Large-diameter part,-   36D Proximal part,-   37 Anisotropically conductive sheet,-   37A Conductive path-forming parts,-   37B Insulating part,-   38 Spacer board,-   38A Through-hole for inspection pin,-   39 wire,-   50 Lower-side board-compressing member,-   50A Through-hole for positioning pin,-   51 Lower-side adaptor,-   52 Circuit board for inspection,-   52A Electrodes for current supply,-   52B Electrodes for voltage measurement,-   52C Terminal electrodes,-   52D Internal wiring part,-   53 Anisotropically conductive sheet,-   55 Lower-side inspection head,-   56 Inspection pins,-   56A Tip part,-   56B Central part,-   56C Large-diameter part,-   56D Proximal part,-   57 Anisotropically conductive sheet,-   58 Spacer board,-   58A Through-hole for inspection pin,-   59 Wire,-   60 Upper-side board-compressing member,-   61 Upper-side adaptor,-   62 Circuit board for inspection,-   62A Inspection electrodes,-   62B Terminal electrodes,-   62C Internal wiring part,-   63 Upper-side inspection head,-   64 Anisotropically conductive sheet,-   65 Lower-side board-compressing member,-   66 Lower-side adaptor,-   67 circuit board for inspection,-   67A Inspection electrodes,-   67B Terminal electrodes,-   67C Internal wiring part,-   68 Lower-side inspection head,-   69 Anisotropically conductive sheet,-   70 Inspection apparatus,-   71 Upper-side inspection head,-   72 Electrode device,-   73 Anisotropically conductive sheet,-   74 Upper-side base plate,-   75 Lower-side inspection head,-   76 Electrode device,-   77 Anisotropically conductive sheet,-   78 Lower-side base plate,-   79 Spacer,-   80 Inspection object circuit board,-   81, 82 Inspection object electrodes,-   83 Power supply device,-   84 Electric signal processor,-   PA, PD Probes for current supply,-   PB, PC Probes for voltage measurement,-   90 Inspection apparatus,-   91A Upper-side board-compressing member,-   91B Lower-side board-compressing member,-   92A, 92B Circuit boards for inspection,-   93A, 93B Anisotropically conductive sheets,-   94A, 94B Supports,-   95A, 95B Support-infixing plates,-   96A, 96B Base plates,-   97A, 97B Supporting points,-   98A, 98B Electrode devices,-   99A, 99B Anisotropically conductive sheets,-   100 Inspection apparatus,-   101A Upper-side board-compressing member,-   101B Lower-side board-compressing member,-   102 Circuit board for inspection,-   102A Inspection electrodes,-   103 Anisotropically conductive sheet,-   104 Supports,-   105 Support-infixing plate,-   106 Base plate,-   107 Circuit board for inspection,-   107A Inspection electrodes,-   108 Electrode device,-   109 Anisotropically conductive sheet.

BEST MODE FOR CARRYING OUT THE INVENTION

The mode for carrying out the present invention will hereinafter bedescribed in detail.

FIG. 1 is a cross-sectional view illustrating the construction of anexemplary inspection apparatus for circuit board according to thepresent invention together with an inspection object circuit board, andFIG. 2 illustrates, on an enlarged scale, a part of the inspectionapparatus for circuit board shown in FIG. 1.

This inspection apparatus (hereinafter also referred to as “firstinspection apparatus”) 10 is used for conducting electrical inspectionof a circuit board by measuring electric resistance between electrodesin the circuit board. In this inspection apparatus, an upper-sideboard-compressing member 30 arranged on an upper side of an inspectionobject circuit board (circuit board to be inspected) 1 and provided withan anisotropically conductive sheet 33 on its front surface (lowersurface in FIG. 1), and a lower-side board-compressing member 50arranged on a lower side of the circuit board 1 to be inspected andprovided with an anisotropically conductive sheet 53 on its frontsurface (upper surface in FIG. 1) are arranged so as to be verticallyopposed to each other.

In the circuit board 1 to be inspected in this embodiment, upper-sideelectrodes 2 to be inspected are formed on its upper surface, andlower-side electrodes 3 to be inspected are formed on its lower surface.These lower-side electrodes 3 to be inspected are electrically connectedto their corresponding upper-side electrodes 2 to be inspected.

Examples of the circuit board 1 to be inspected include those havingflexibility, such as printed boards.

The degree of flexibility required of the circuit board 1 to beinspected is as follows.

When the circuit board 1 to be inspected is horizontally arranged in astate that both ends of the circuit board 1 to be inspected have beensupported at intervals of 10 cm as illustrated in FIG. 3, deflection aof the circuit board 1 to be inspected caused by pressurizing it by apressure of 50 kgf from above is preferably at least 0.04% of the widthb of the circuit board 1 to be inspected.

The upper-side board-compressing member 30 is provided on a frontsurface (lower surface in FIG. 1) of an upper-side base plate 21supported by a plurality (4 supports are illustrated in FIG. 1) ofupper-side supports 22 infixed into a flat plate-like upper-sidesupport-infixing plate 23 composed of, for example, a laminate (tradename: “SUMILITE”, product of SUMITOMO BAKELITE Co., Ltd.) of a phenolresin containing a fine thread cloth and vertically extending from theupper-side support-infixing plate 23.

In the embodiment illustrated, engaging recesses (not illustrated) eachhaving an inner diameter fitted to an outer diameter of a tip part 22Bof the upper-side support 22 are formed at positions where upper-sidesupporting points 21A, which will be described subsequently, should beformed, in a back surface (upper surface in FIG. 1) of the upper-sidebase plate 21. Engaging portions of the tip parts 22B of the upper-sidesupports 22 are inserted into and engaged with these engaging recesses,whereby the upper-side supporting points 21A are formed by theupper-side supports 22 on the upper-side base plate 21.

The lower-side board-compressing member 50 is provided on a frontsurface (upper surface in FIG. 1) of a lower-side base plate 25supported by a plurality (3 supports are illustrated in FIG. 1) oflower-side supports 26 infixed into a flat plate-like lower-sidesupport-infixing plate 27 composed of, for example, a laminate (tradename: “SUMILITE”, product of SUMITOMO BAKELITE Co., Ltd.) of a phenolresin containing a fine thread cloth and vertically extending from thelower-side support-infixing plate 27.

In the embodiment illustrated, a substantially rectangular projectedparts 25A (see FIG. 10) are formed in the whole region, in which aplurality of inspection pins 56 are arranged, on the front surface ofthe lower-side base plate 25. In a back surface (lower surface inFIG. 1) corresponding to the projected part 25A of the lower-side baseplate 25, engaging recesses (not illustrated) each having an innerdiameter fitted to an outer diameter of a tip part 26B of the lower-sidesupport 26 are formed at positions where lower-side supporting points25B, which will be described subsequently, should be formed. Engagingportions of the tip parts 26B of the lower-side supports 26 are insertedinto and engaged with these engaging recesses, whereby the lower-sidesupporting points 25B are formed by the lower-side supports 26 on thelower-side base plate 25.

Incidentally, the engaging recesses in both upper-side base plate 21 andlower-side base plate 25 are not essential, and no engaging recess maybe formed in each base plate.

The upper-side supporting point 21A related to the upper-sideboard-compressing member 30 and the lower-side supporting point 25Brelated to the lower-side board-compressing member 50 are arranged atdifferent positions on a plane of projection (hereinafter also referredto as “specific plane of projection”) in a thickness-wise direction ofthe upper-side board-compressing member 30 and lower-sideboard-compressing member 50 when the first inspection apparatus 10 isseen through from above (from above in FIG. 1).

The upper-side supporting points 21A and the lower-side supportingpoints 25B are preferably formed in the form of a lattice on theupper-side base plate 21 and on the lower-side base plate 25,respectively, as shown in the embodiment illustrated.

Specifically, the upper-side supporting points 21A and the lower-sidesupporting points 25B are arranged in such a manner that as illustratedin FIG. 4, on the specific plane M1 of projection, only one lower-sidesupporting point 25B is arranged at a position where 2 diagonal linesintersect within a rectangular upper-side unit region R1 partitioned byadjacent 4 upper-side supporting points 21A, and only one upper-sidesupporting point 21A is arranged at a position where 2 diagonal linesintersect within a rectangular lower-side unit region R2 partitioned byadjacent 4 lower-side supporting points 25B. In FIG. 4, the upper-sidesupporting points 21A and the lower-side supporting points 25B areindicated by a black circle and a white circle, respectively, and oneupper-side unit region R1 and one lower-side unit regions R2 are eachsurrounded by an alternate long and short dashed line.

In the inspection apparatus, clearances between upper-side supportingpoints 21A adjacent to each other and between lower-side supportingpoints 25B adjacent to each other are each preferably 10 to 100 mm, morepreferably 12 to 70 mm, particularly preferably 15 to 50 mm.

Those having flexibility are used as the upper-side base plate 21 andlower-side base plate 25.

The degree of flexibility required of the upper-side base plate 21 andlower-side base plate 25 (hereinafter also referred to as “specific baseplates”) is as follows.

When the specific base plate is horizontally arranged in a state thatboth ends of the specific base plate have been supported at intervals of10 cm (see FIG. 3), deflection of the specific base plate caused bypressurizing it by a pressure of 50 kgf from above is preferably atleast 0.02% of the width of the specific base plate, and it preferablyundergoes neither breakage nor permanent set even when it is pressurizedby a pressure of 50 kgf from above.

More specifically, as a material for the upper-side base plate 21 andlower-side base plate 25, is used an insulating material having aresistivity of at least 1×10¹⁰ Ω·cm, for example, a resin materialhaving high mechanical strength, such as a polyimide resin, polyesterresin, polyamide resin, phenol resin, polyacetal resin, poly(butyleneterephthalate) resin, poly(ethylene terephthalate) resin, syndiotacticpolystyrene resin, poly(phenylene sulfide) resin, poly(ether ethylketone) resin, fluorocarbon resin, poly(ether nitrile) resin, poly(ethersulfone) resin, polyacrylate resin or polyamide-imide resin, a glassfiber-reinforced composite resin material such as a glassfiber-reinforced epoxy resin, glass fiber-reinforced polyester resin,glass fiber-reinforced polyimide resin, glass fiber-reinforced phenolresin or glass fiber-reinforced fluorocarbon resin, a carbonfiber-reinforced composite resin such as a carbon fiber-reinforced epoxyresin, carbon fiber-reinforced polyester resin, carbon fiber-reinforcedpolyimide resin, carbon fiber-reinforced phenol resin or carbonfiber-reinforced fluorocarbon resin, a composite resin material obtainedby filling an inorganic material such as silica, alumina or boronnitride into an epoxy resin, phenol resin or the like, or a compositeresin material obtained by containing mesh in an epoxy resin, phenolresin or the like. A composite plate material formed by laminating aplurality of plates composed of any of these materials may also be used.

The thickness of each of the upper-side base plate 21 and lower-sidebase plate 25 is suitably selected according to the kind of the materialforming the upper-side base plate 21 or lower-side base plate 25.However, it is, for example, 1 to 10 mm.

In the embodiment illustrated, “the thickness of the lower-side baseplate 25” indicates a thickness of a portion where the projected part25A is formed. The projected height of this projected part 25A ispreferably 0.5 to 5 mm.

In particular, when each of the upper-side base plate 21 and lower-sidebase plate 25 has the construction that through-holes are formed as thefirst inspection apparatus 10, the thickness thereof is preferably atmost 5 mm.

When the thickness of a base plate, in which through-holes should beformed, is 5 mm or thinner, through-holes can be formed with highefficiency by one drilling operation without involving bad effects suchas damage or breakage of a drill bit, thereby it is unnecessary toconduct the drilling operation plural times for forming onethrough-hole. Accordingly, the inspection apparatus equipped with baseplates having a thickness of 5 or thinner can shorten the time requiredfor the drilling operation compared with an inspection apparatusequipped with thick base plates and moreover can be produced with highproduction efficiency because the through-holes can be formed with highefficiency.

Specific preferable examples of the upper-side base plate 21 andlower-side base plate 25 include those composed of a glassfiber-reinforced epoxy resin and having a thickness of 2 to 5 mm.

As the upper-side supports 22 and lower-side supports 26, may be usedcolumnar bodies composed of a material such as brass, aluminum,titanium, stainless steel, copper, iron or an alloy thereof.

These upper-side supports 22 and lower-side supports 26 preferably havean overall length of 10 to 100 mm.

A plurality of the upper-side supports 22 making up the first inspectionapparatus 10 may have different overall lengths so far as they arecapable of achieving a specific measurable state. Likewise, a pluralityof the lower-side supports 26 may have different overall lengths.

An outer diameter of a tip part 22B forming the upper-side supportingpoints 21A or a tip part 26B forming the lower-side supporting points25B is preferably 1 to 10 mm, respectively, and the outer diameter ofthe tip part 22B of the upper-side support 22 is preferably the same asthe outer diameter of the tip part 26B of the lower-side support 26.

In the embodiment illustrated, each upper-side support 22 is composed ofa proximal part 22A fixed to the upper-side base plate 21 and a tip part22B that is continuous with this proximal part 22A, forms an upper-sidesupporting point 21A by its tip surface and has a diameter smaller thanthe proximal part 22A. On the other hand, each lower-side support 26 iscomposed of a proximal part 26A fixed to the lower-side base plate 25and a tip part 26B that is continuous with this proximal part 26A, formsan lower-side supporting point 25B by its tip surface and has a diametersmaller than the proximal part 26A. These upper-side support 22 andlower-side support 26 are those having the tip parts 22B and 26B of thesame outer diameter.

The upper-side board-compressing member 30 making up the firstinspection apparatus 10 is constructed by arranging an upper-sideadaptor 31 and an upper-side inspection head 35 in this order from belowin FIG. 1.

As illustrated in FIG. 5, the upper-side adaptor 31 is constructed by acircuit board 32 for inspection and an elastic anisotropicallyconductive sheet 33 arranged on a front surface (lower surface in FIGS.1 and 5) of the circuit board 32 for inspection by being fixed by aproper means.

On the front surface of the circuit board 32 for inspection in theupper-side adaptor 31, electrodes 32A for current supply and electrodes32B for voltage measurement making up an inspection electrode pair are,in a state separated from each other, arranged in accordance with anarrangement pattern of the upper-side electrodes 2 to be inspected onthe upper surface of the circuit board 1 to be inspected so as to belocated, in relation with one upper-side electrode 2 to be inspected,within a region of an area equal to a region occupied by the upper-sideelectrode 2 to be inspected as illustrated in FIG. 6.

In FIG. 6, reference numeral 32E designates a positioning hole.

A clearance between the electrode 32A for current supply and theelectrode 32B for voltage measurement in the circuit board 32 forinspection is preferably at least 10 μm. If this clearance is shorterthan 10 μm, a current flowing between the electrode 32A for currentsupply and the electrode 32B for voltage measurement through theanisotropically conductive sheet 33 becomes high, so that it may bedifficult in some cases to measure electric resistance with highprecision.

On the other hand, the upper limit of the clearance is determined by thesizes of the respective inspection electrodes and the size and pitch oftheir related upper-side electrodes 2 to be inspected, and is generallyat most 500 μm. If this clearance is too large, it is difficult tosuitably arrange both inspection electrodes correspondingly to onesmall-sized upper-side electrode 2 to be inspected.

On a back surface (upper surface in FIGS. 1 and 5) of the circuit board32 for inspection, a plurality of terminal electrodes 32C are arrangedaccording to positions of lattice points having a pitch of, for example,0.2 mm, 0.3 mm, 0.45 mm, 0.5 mm, 0.75 mm, 0.8 mm, 1.06 mm, 1.27 mm, 1.5mm, 1.8 mm or 2.54 mm as illustrated in FIG. 7. These terminalelectrodes 32C are each electrically connected to its correspondingelectrode 32A for current supply or electrode 32B for voltagemeasurement through an internal wiring part 32D.

The anisotropically conductive sheet 33 in the upper-side adaptor 31 isthe so-called dispersion type anisotropically conductive sheet thatconductive particles P are contained in a base material composed of anelastic polymeric substance having insulating property in a stateoriented so as to align in a thickness-wise direction of theanisotropically conductive sheet 33, and conductive paths are formed bychains of the conductive particles P when the sheet is pressurized inthe thickness-wise direction in the measurable state.

In this description, the term “measurable state” means a state that thecircuit board 1 to be inspected is compressed between, for example, theupper-side board-compressing member 30 and the lower-sideboard-compressing member 50, whereby the anisotropically conductivesheet is pressed in the thickness-wise direction thereof.

The anisotropically conductive sheet 33 preferably has higherconductivity in its thickness-wise direction than that in a planedirection perpendicular to the thickness-wise direction. Specifically,the anisotropically conductive sheet preferably has electricalproperties that a ratio of the electric resistance value in the planedirection to the electric resistance value in the thickness-wisedirection is 1 or lower, particularly 0.5 or lower.

If the ratio exceeds 1, a current flowing between the electrode 32A forcurrent supply and the electrode 32B for voltage measurement throughsuch an anisotropically conductive sheet 33 becomes high, so that it maybe difficult in some cases to measure electric resistance with highprecision.

The upper-side inspection head 35 has a plurality of inspection pins 36arranged at positions of lattice points of the same pitch as theterminal electrodes 32C of the upper-side adaptor 31, and an elasticanisotropically conductive sheet 37 is arranged on a front surface(lower surface in FIG. 1) of the head by being fixed by a proper means.

Each of the inspection pins 36 is composed of a columnar tip part 36A, acentral part 36B, which is continuous with the tip part 36A and has adiameter larger than the tip part 36A, a large-diameter part 36C, whichis continuous with the central part 36B and has a diameter larger thanthe central part 36B, and a proximal part 36D, which is continuous withthe large-diameter part 36C and has the same outer diameter as thecentral part 36B as illustrated in FIG. 9.

This inspection pin 36 is fixed in a state that the tip part 36A hasbeen projected from a front surface (lower surface in FIG. 9) of aplate-like spacer board 38 arranged on a front surface (lower surface inFIG. 9) of the upper-side base plate 21 by inserting the proximal part36D of the inspection pin 36 into a through-hole 21B for inspection pinin the upper-side base plate 21, which has an inner diameter fitted tothe outer diameter of the proximal part 36D and is formed at a positionof a lattice point having a pitch, at which the inspection pin 36 shouldbe arranged, and inserting the central part 36B and large-diameter part36C of the inspection pin 36 into a through-hole 38A for inspection pinformed in the spacer board 38 and having a form fitted to the centralpart 36B and large-diameter part 36C.

Each of the inspection pins 36 is electrically connected to a connector(not illustrated) provided on the upper-side support-infixing plate 23through a wire 39 electrically connected to the proximal part 36D andfurther electrically connected to a tester (not illustrated) through theconnector.

The anisotropically conductive sheet 37 in the upper-side inspectionhead 35 is the so-called uneven distribution type anisotropicallyconductive sheet composed of conductive path-forming parts 37A withconductive particles P contained at a high density in a base materialcomposed of an elastic polymeric substance having insulating property,and an insulating part 37B that the conductive particles P do not existat all or scarcely exist in a base material composed of an elasticpolymeric substance having insulating property, and having theconstruction that a plurality of columnar conductive path-forming parts37A formed in accordance with a pattern corresponding to the terminalelectrodes 32C and each having a surface of an area equal to a regionoccupied by the terminal electrode 32C are mutually insulated by theinsulating part 37B. When the conductive path-forming parts 37A arebrought into contact with the surfaces (upper surfaces in FIG. 5) oftheir corresponding terminal electrodes 32C and pressurized in thethickness-wise direction thereof in the measurable state, conductivepaths are formed by respective chains of the conductive particles P.

In the embodiment illustrated, the anisotropically conductive sheet 37has an irregular shape that the surfaces (lower surfaces in FIG. 5) ofthe conductive path-forming parts 37A are projected from the surface(lower surface in FIG. 5) of the insulating part 37B on one surface(lower surface in FIG. 5) of the side of the circuit board 32 forinspection.

The upper-side board-compressing member 30 of the construction describedabove can be constructed by arranging the spacer board 38, in which aplurality of the through-holes 38A for inspection pin have been formed,the anisotropically conductive sheet 37, the circuit board 32 forinspection and the anisotropically conductive sheet 33 at prescribedpositions in this order on the front surface of the upper-side baseplate 21 in a state that the inspection pins 36 have been inserted intothe through-holes 21B for inspection pin formed by the drillingoperation.

The lower-side board-compressing member 50 making up the firstinspection apparatus 10 is constructed by arranging a lower-side adaptor51 and a lower-side inspection head 55 in this order from above in FIG.1.

In the embodiment illustrated, the lower-side board-compressing member50 has a circuit board-holding mechanism for holding the circuit board 1to be inspected in an inspection-executing region 11 formed between theupper-side board-compressing member 30 and the lower-sideboard-compressing member 50. In this circuit board-holding mechanism,positioning pins 13 for arranging the circuit board 1 to be inspected atan exact position in the inspection-executing region 11 are provided ina state that they have been fixed to an alignment movable plate 15located between the lower-side inspection head 55 and the lower-sidebase plate 25 and each have been inserted through a through-hole 50A forpositioning pin formed in the lower-side board-compressing member 50 anda through-hole 25C for positioning pin formed in the lower-side baseplate 25.

The alignment movable plate 15 has a thickness fitted to the projectedheight of the projected part 25A of the lower-side base plate 25 and issupported by an alignment support 16 movably fixed to the lower-sidebase plate 25. The alignment movable plate 15 is arranged in a statethat the projected part 25A of the lower-side base plate 25 has beeninserted into a substantially rectangular hole 15A formed at a positioncorresponded to the projected part 25A and having a size fitted to theprojected part 25A as illustrated in FIG. 10.

The lower-side adaptor 51 is constructed by a circuit board 52 forinspection and an elastic anisotropically conductive sheet 53 arrangedon a front surface (upper surface in FIG. 1) of the circuit board 52 forinspection by being fixed by a proper means.

On the front surface of the circuit board 52 for inspection in thelower-side adaptor 51, electrodes 52A for current supply and electrodes52B for voltage measurement making up an inspection electrode pair are,in a state separated from each other, arranged in accordance with anarrangement pattern of the lower-side electrodes 3 to be inspected onthe lower surface of the circuit board 1 to be inspected so as to belocated, in relation with one lower-side electrode 3 to be inspected,within a region of an area equal to a region occupied by the lower-sideelectrode 3 to be inspected.

A clearance between the electrode 52A for current supply and theelectrode 52B for voltage measurement in the circuit board 52 forinspection is preferably at least 10 μm. If this clearance is shorterthan 10 μm, a current flowing between the electrode 52A for currentsupply and the electrode 52B for voltage measurement through theanisotropically conductive sheet 53 becomes high, so that it may bedifficult in some cases to measure electric resistance with highprecision.

On the other hand, the upper limit of the clearance is determined by thesizes of the respective inspection electrodes and the size and pitch oftheir related lower-side electrodes 3 to be inspected, and is generallyat most 500 μm. If this clearance is too large, it is difficult tosuitably arrange both inspection electrodes correspondingly to onesmall-sized lower-side electrode 3 to be inspected.

On a back surface (lower surface in FIG. 1) of the circuit board 52 forinspection, a plurality of terminal electrodes 52C are arrangedaccording to positions of lattice points having a pitch of, for example,0.2 mm, 0.3 mm, 0.45 mm, 0.5 mm, 0.75 mm, 0.8 mm, 1.06 mm, 1.27 mm, 1.5mm, 1.8 mm or 2.54 mm. These terminal electrodes 52C are eachelectrically connected to its corresponding electrode 52A for currentsupply or electrode 52B for voltage measurement through an internalwiring part 52D.

The anisotropically conductive sheet 53 in the lower-side adaptor 51 isthe so-called dispersion type anisotropically conductive sheet thatconductive particles P are contained in a base material composed of anelastic polymeric substance having insulating property in a stateoriented so as to align in a thickness-wise direction of theanisotropically conductive sheet 53, and conductive paths are formed bychains of the conductive particles when the sheet is pressurized in thethickness-wise direction in the measurable state.

The anisotropically conductive sheet 53 preferably has higherconductivity in its thickness-wise direction than that in a planedirection perpendicular to the thickness-wise direction. Specifically,the anisotropically conductive sheet preferably has electricalproperties that a ratio of the electric resistance value in the planedirection to the electric resistance value in the thickness-wisedirection is 1 or lower, particularly 0.5 or lower.

If the ratio exceeds 1, a current flowing between the electrode 52A forcurrent supply and the electrode 52B for voltage measurement through theanisotropically conductive sheet 53 becomes high, so that it may bedifficult in some cases to measure electric resistance with highprecision.

The lower-side inspection head 55 has a plurality of inspection pins 56arranged at positions of lattice points of the same pitch as theterminal electrodes 52C of the lower-side adaptor 51, and an elasticanisotropically conductive sheet 57 is arranged on a front surface(upper surface in FIG. 1) of the head by being fixed by a proper means.

Each of the inspection pins 56 is composed of a columnar tip part 56A, acentral part 56B, which is continuous with the tip part 56A and has adiameter larger than the tip part 56A, a large-diameter part 56C, whichis continuous with the central part 56B and has a diameter larger thanthe central part 56B, and a proximal part 56D, which is continuous withthe large-diameter part 56C and has the same outer diameter as thecentral part 56B as illustrated in FIG. 11.

This inspection pin 56 is fixed in a state that the tip part 56A hasbeen projected from a front surface (upper surface in FIG. 11) of aspacer board 58 arranged on a front surface (upper surface in FIG. 11)of the lower-side base plate 25 by inserting the proximal part 56D ofthe inspection pin 56 into a through-hole 25D for inspection pin in thelower-side base plate 25, which has an inner diameter fitted to theouter diameter of the proximal part 56D and is formed at a position of alattice point having a pitch, at which the inspection pin 56 should bearranged, and inserting the central part 56B and large-diameter part 56Cof the inspection pin 56 into a through-hole 58A for inspection pinformed in the spacer board 58 and having a form fitted to the centralpart 56B and large-diameter part 56C.

Each of the inspection pins 56 is electrically connected to a connector(not illustrated) provided on the lower-side support-infixing plate 27through a wire 59 electrically connected to the proximal part 56D andfurther electrically connected to a tester (not illustrated) through theconnector.

The anisotropically conductive sheet 57 in the lower-side inspectionhead 55 has the same construction as the anisotropically conductivesheet 37 in the upper-side inspection head 35 and is the so-calleduneven distribution type anisotropically conductive sheet composed ofconductive path-forming parts with conductive particles contained at ahigh density in a base material composed of an elastic polymericsubstance having insulating property, and an insulating part that theconductive particles do not exist at all or scarcely exist in a basematerial composed of an elastic polymeric substance having insulatingproperty, and having the construction that a plurality of columnarconductive path-forming parts formed in accordance with a patterncorresponding to the terminal electrodes 52C and each having a surfaceof an area equal to a region occupied by the terminal electrode 52C aremutually insulated by the insulating part. When the conductivepath-forming parts are brought into contact with the surfaces of theircorresponding terminal electrodes 52C and pressurized in thethickness-wise direction thereof in the measurable state, conductivepaths are formed by respective chains of the conductive particles.

In this embodiment, the anisotropically conductive sheet 57 has anirregular shape that the surfaces of the conductive path-forming partsare projected from the surface of the insulating part on one surface ofthe side of the circuit board 52 for inspection.

The lower-side board-compressing member 50 of the construction describedabove can be constructed by arranging the alignment movable plate 15, inwhich the substantially rectangular hole 15A has been formed, the spacerboard 58, in which a plurality of the through-holes 58A for inspectionpin have been formed, the anisotropically conductive sheet 57, thecircuit board 52 for inspection and the anisotropically conductive sheet53 at prescribed positions in this order on the front surface of thelower-side base plate 25 in a state that the inspection pins 56 havebeen inserted into the through-holes 21B for inspection pin formed atthe projected part 25A by the drilling operation.

The elastic polymeric substances forming the base materials of theanisotropically conductive sheets making up the first inspectionapparatus 10 are preferably polymeric substances having a crosslinkedstructure. As curable polymeric substance-forming materials usable forobtaining crosslinked polymeric substances, may be used variousmaterials. Specific examples thereof include conjugated diene rubberssuch as polybutadiene rubber, natural rubber, polyisoprene rubber,styrene-butadiene copolymer rubber and acrylonitrile-butadiene copolymerrubber, and hydrogenated products thereof; block copolymer rubbers suchas styrene-butadiene-diene block terpolymer rubber and styrene-isopreneblock copolymers, and hydrogenated products thereof; and besideschloroprene, urethane rubber, polyester rubber, epichlorohydrin rubber,silicone rubber, ethylene-propylene copolymer rubber andethylene-propylene-diene terpolymer rubber.

When weather resistance is required of the resulting anisotropicallyconductive sheet in the embodiment described above, any other materialthan conjugated diene rubbers is preferably used. In particular,silicone rubber is preferably used from the viewpoints of forming andprocessing ability and electrical properties.

As the silicone rubber, is preferred that obtained by crosslinking orcondensing liquid silicone rubber. The liquid silicone rubber preferablyhas a viscosity not higher than 10⁵ poises as measured at a shear rateof 10⁻¹ sec and may be any of condensation type, addition type and thosecontaining a vinyl group or hydroxyl group. As specific examplesthereof, may be mentioned dimethyl silicone raw rubber, methylvinylsilicone raw rubber and methylphenylvinyl silicone raw rubber.

Among these, vinyl group-containing liquid silicone rubber (vinylgroup-containing dimethyl polysiloxane) is generally obtained bysubjecting dimethyldichlorosilane or dimethyldialkoxysilane tohydrolysis and condensation reaction in the presence ofdimethylvinylchlorosilane or dimethylvinylalkoxysilane and successivelyfractionating the reaction product by, for example, repeateddissolution-precipitation.

Liquid silicone rubber having vinyl groups at both terminals thereof isobtained by subjecting a cyclic siloxane such asoctamethylcyclotetrasiloxane to anionic polymerization in the presenceof a catalyst, using, for example, dimethyldivinylsiloxane as apolymerization terminator and suitably selecting other reactionconditions (for example, amounts of the cyclic siloxane andpolymerization terminator). As the catalyst for the anionicpolymerization, may be used an alkali such as tetramethylammoniumhydroxide or n-butylphosphonium hydroxide or a silanolate solutionthereof. The reaction is conducted at a temperature of, for example, 80to 130° C.

On the other hand, hydroxyl group-containing liquid silicone rubber(hydroxyl group-containing dimethyl polysiloxane) is generally obtainedby subjecting dimethyldichlorosilane or dimethyldialkoxysilane tohydrolysis and condensation reaction in the presence ofdimethylhydrochlorosilane or dimethylhydroalkoxysilane and successivelyfractionating the reaction product by, for example, repeateddissolution-precipitation.

The hydroxyl group-containing liquid silicone rubber is also obtained bysubjecting a cyclic siloxane to anionic polymerization in the presenceof a catalyst, using, for example, dimethylhydrochlorosilane,methyldihydrochlorosilane or dimethylhydroalkoxysilane as apolymerization terminator and suitably selecting other reactionconditions (for example, amounts of the cyclic siloxane andpolymerization terminator). As the catalyst for the anionicpolymerization, may be used an alkali such as tetramethylammoniumhydroxide or n-butylphosphonium hydroxide or a silanolate solutionthereof. The reaction is conducted at a temperature of, for example, 80to 130° C.

Such an elastic polymeric substance preferably has a molecular weight Mw(weight average molecular weight as determined in terms of standardpolystyrene equivalent) of 10,000 to 40,000. It also preferably has amolecular weight distribution index (a ratio Mw/Mn of weight averagemolecular weight Mw as determined in terms of standard polystyreneequivalent to number average molecular weight Mn as determined in termsof standard polystyrene equivalent) of at most 2 from the viewpoint ofheat resistance of the resulting anisotropically conductive sheet.

In the above, a curing catalyst for curing the polymericsubstance-forming material may be contained in the sheet-formingmaterial for obtaining the anisotropically conductive sheet. As such acuring catalyst, may be used an organic peroxide, fatty acid azocompound, hydrosilylated catalyst or the like.

Specific examples of the organic peroxide used as the curing catalystinclude benzoyl peroxide, bisdicyclobenzoyl peroxide, dicumyl peroxideand di-tert-butyl peroxide.

Specific examples of the fatty acid azo compound used as the curingcatalyst include azobisisobutyronitrile.

Specific examples of that used as the catalyst for hydrosilylationreaction include publicly known catalysts such as platinic chloride andsalts thereof, platinum-unsaturated group-containing siloxane complexes,vinylsiloxane-platinum complexes,platinum-1,3-divinyltetramethyldisiloxane complexes, complexes oftriorganophosphine or triorganophosphite and platinum, acetyl acetateplatinum chelates, and cyclic diene-platinum complexes.

The amount of the curing catalyst used is suitably selected in view ofthe kind of the polymeric substance-forming material, the kind of thecuring catalyst and other curing treatment conditions. However, it isgenerally 3 to 15 parts by mass per 100 parts by mass of the polymericsubstance-forming material.

In the sheet-forming material, as needed, may be contained an ordinaryinorganic filler such as silica powder, colloidal silica, aerogel silicaor alumina. By containing such an inorganic filler, the thixotropicproperty of such a sheet-forming material is ensured, the viscositythereof becomes high, the dispersion stability of the conductiveparticles is improved, and moreover the strength of the resultinganisotropically conductive sheet can be made high.

No particular limitation is imposed on the amount of such an inorganicfiller used. However, the use in a too great amount is not preferredbecause the orientation of the conductive particles by a magnetic fieldcannot be sufficiently achieved.

The viscosity of the sheet-forming material is preferably within a rangeof 100,000 to 1,000,000 cP at a temperature of 25° C.

As the conductive particles, those exhibiting magnetism are used fromthe viewpoint of permitting them to be easily oriented so as to align ina thickness-wise direction of the resulting anisotropically conductivesheet by applying a magnetic field. Specific examples of such conductiveparticles include particles of metals exhibiting magnetism, such asnickel, iron and cobalt and particles of alloys thereof, particlescontaining such a metal, particles obtained by using these particles ascore particles and plating surfaces of the core particles with a metalhaving good conductivity, such as gold, silver, palladium or rhodium,particles obtained by using particles of a non-magnetic metal, particlesof an inorganic substance, such as glass beads, or particles of apolymer as core particles and plating surfaces of the core particleswith a conductive magnetic substance such as nickel or cobalt, andparticles obtained by coating the core particles with both conductivemagnetic substance and metal having good conductivity.

Among these, particles obtained by using particles composed of aferromagnetic substance, for example, nickel particles as core particlesand plating their surfaces with a metal having good conductivity,particularly gold are preferably used.

No particular limitation is imposed on a means for coating the surfacesof the core particles with the conductive metal. However, the coatingmay be conducted by, for example, chemical plating or electroplating.

When those obtained by coating the surfaces of the core particles withthe conductive metal are used as the conductive particles, the coatingrate (proportion of an area coated with the conductive metal to thesurface area of the core particles) of the conductive metal on theparticle surfaces is preferably at least 40%, more preferably at least45%, particularly preferably 47 to 95% from the viewpoint of achievinggood conductivity.

The amount of the conductive metal to coat is preferably 0.5 to 50% bymass, more preferably 1 to 30% by mass, still more preferably 3 to 25%by mass, particularly preferably 4 to 20% by mass based on the coreparticles. When the conductive metal to coat is gold, the coating amountthereof is preferably 2.5 to 30% by mass, more preferably 3 to 20% bymass, still more preferably 3.5 to 17% by mass based on the coreparticles.

The water content in the conductive particles is preferably at most 5%,more preferably at most 3%, still more preferably at most 2%,particularly preferably at most 1%. The use of conductive particlessatisfying such conditions prevents or inhibits occurrence of bubblesupon a curing treatment of the polymeric substance-forming material.

The conductive particles are preferably contained in a proportion of 5to 60%, more preferably 8 to 50%, particularly preferably 10 to 40% interms of volume fraction.

The electric resistance in the thickness-wise direction of theanisotropically conductive sheet is preferably at most 100 mΩ in a statethat the anisotropically conductive sheet has been pressurized in thethickness-wise direction under a load of 10 to 20 gf.

The thickness of each of the anisotropically conductive sheet 33 makingup the upper-side adaptor 31, and the anisotropically conductive sheet53 making up the lower-side adaptor 51 is preferably 0.05 to 0.2 mm.

The thickness of each of the anisotropically conductive sheet 37 makingup the upper-side inspection head 35, and the anisotropically conductivesheet 57 making up the lower-side inspection head 55 is preferably 0.1to 1.5 mm.

The thickness of each of the anisotropically conductive sheets 37 and 57means a thickness of each conductive path-forming part; and theprojected height of the conductive path-forming part from the surface ofthe insulating part is preferably 0.02 to 1.3 mm.

The dispersion type anisotropically conductive sheets making up thefirst inspection apparatus 10 can be produced in the following manner.

A flowable sheet-forming material is prepared by dispersing conductiveparticles in a polymeric substance-forming material, which will becomean elastic polymeric substance by a curing treatment, and conducting adefoaming treatment by pressure reduction as needed. This sheet-formingmaterial prepared in such a manner is poured into a molding cavity of amold for molding of an anisotropically conductive sheet to form asheet-forming material layer in a state that the conductive particleshave been dispersed. For example, a pair of electromagnets are thenarranged on an upper surface and a lower surface of the mold, and theelectromagnets are operated, thereby applying a parallel. magnetic fieldto the sheet-forming material layer in its thickness-wise direction toorient the conductive particles dispersed in the sheet-forming materiallayer so as to align in the thickness-wise direction. In this state, thesheet-forming material layer is subjected to a curing treatment, therebyproducing an anisotropically conductive sheet with the conductiveparticles oriented in the elastic polymeric substance so as to align inthe thickness-wise direction.

The uneven distribution type anisotropically conductive sheets making upthe first inspection apparatus 10 can be produced in the followingmanner. For example, a mold for molding of anisotropically conductivesheet, which is composed of a top force and a bottom force each having aform of a substantially flat plate as a whole and corresponding to eachother, and has the construction that a material layer filled into amolding cavity between the top force and the bottom force can be curedby heating while applying a magnetic field to the material layer, isprovided.

In order to form portions having conductivity at proper positions byapplying a magnetic field to the material layer, in this mold formolding of the anisotropically conductive sheet, both top force andbottom force have the construction having a mosaic layer formed byarranging ferromagnetic substance portions formed of iron, nickel or thelike for causing an intensity distribution in the magnetic field withinthe mold and non-magnetic portions formed of a non-magnetic metal suchas copper, or a resin alternatively so as to adjoin each other on a baseplate composed of a ferromagnetic substance such as iron or nickel. Theferromagnetic substance portions are arranged in accordance with apattern corresponding to a pattern of conductive path-forming parts tobe formed.

The molding surface of the top force is flat, while the molding surfaceof the bottom force has slight irregularities corresponding to theconductive path-forming parts to be formed in the anisotropicallyconductive sheet.

The above-described mold for molding the anisotropically conductivesheet is used to produce an anisotropically conductive sheet in thefollowing manner.

A molding material obtained by containing conductive particlesexhibiting magnetism in a polymeric substance-forming material, whichwill become an elastic polymeric substance by being cured, is firstfilled into the molding cavity of the mold for molding theanisotropically conductive sheet to form a molding material layer.

The ferromagnetic substance portions and non-magnetic substance portionsin each of the top force and the bottom force are then utilized to applya magnetic field having an intensity distribution to the moldingmaterial layer formed in the thickness-wise direction thereof, therebygathering the conductive particles between the ferromagnetic substanceportions in the top force and the ferromagnetic substance portions inthe bottom force located right below the portions of the top force by aneffect of magnetic force, and further orienting the conductive particlesso as to align in the thickness-wise direction. In that state, themolding material layer is subjected to a curing treatment, therebyproducing anisotropically conductive sheet having the construction thata plurality of columnar conductive path-forming parts are mutuallyinsulated by an insulating part.

The first inspection apparatus 10 is not limited to the constructionthat the anisotropically conductive sheets are separately produced, andthe sheets produced are arranged on other component members, forexample, the circuit boards for inspection, and may be such that thesesheets are integrated with other component members in the productionprocess thereof.

In the first inspection apparatus 10 of the construction describedabove, electrical inspection of the circuit board 1 to be inspected isperformed in the following manner.

The circuit board 1 to be inspected is arranged in theinspection-executing region 11 by the circuit board-holding mechanism.In this state, the upper-side support-infixing plate 23 and thelower-side support-infixing plate 27 are respectively moved indirections approaching to the circuit board 1 to be inspected, wherebythe upper-side supports 22 and lower-side support 26 press theupper-side base plate 21 and the lower-side base plate 25, respectively,thereby moving the upper-side board-compressing member 30 and thelower-side board-compressing member 50 in directions approaching to thecircuit board 1 to be inspected. As a result, the circuit board 1 to beinspected is compressed by the upper-side board-compressing member 30and the lower-side board-compressing member 50.

As illustrated in FIG. 12, a complex stack 19 composed of the circuitboard 1 to be inspected, and the upper-side board-compressing member 30and lower-side board-compressing member 50 which compress the circuitboard, is deflected by being shifted in the thickness-wise directiontogether with the upper-side base plate 21 and lower-side base plate 25,at positions, over the whole body, respectively pressed by theupper-side supports 22 and lower-side supports 26 in accordance with theupper-side supporting points 21A and lower-side supporting points 25B,and deformed in the form of a regular wave shape to bring about ameasurable state.

Even in the measurable state, the alignment movable plate 15 is in astate slidable with the movement of the alignment support 16 as in anon-measurable state.

The first inspection apparatus 10 is so constructed that in such ameasurable state, a gap (hereinafter also referred to as “gap betweenupper-side and low-side supports”) in the thickness-wise direction ofthe complex stack 19 between a tip level (hereinafter also referred toas “upper-side level”) in the upper-side support 22 and a tip level(hereinafter also referred to as “lower-side level”) in the lower-sidesupport 26 is smaller than the total thickness of the complex stack 19,the upper-side base plate 21 and the lower-side base plate 25.

In the above, “the thickness of the complex stack 19” means the totalthickness of the upper-side board-compressing member 30, the circuitboard 1 to be inspected and the lower-side board-compressing member 50.

In the above, “the gap between upper-side and lower-side supports” meansa clearance between a boundary surface (hereinafter also referred to as“upper-side boundary surface”) M2 between the upper-side support 22 andthe upper-side base plate 21 located on the upper-side level and aboundary surface (hereinafter also referred to as “lower-side boundarysurface”) M3 between the lower-side support 26 and the lower-side baseplate 25 located on the lower-side level in a direction perpendicular tothe thickness-wise direction of the complex stack 19 when the upper-sideboundary surface M2 is located above the lower-side boundary surface M3in FIG. 12. Accordingly, in this description, the case where thepositional relation between the upper-side boundary surface M2 and thelower-side boundary surface M3 is reversed is regarded as a state thatthere is no gap between upper-side and lower-side supports.

If the gap between upper-side and lower-side supports is too great, thecomplex stack 19 cannot be deformed together with the upper-side baseplate 21 and lower-side base plate 25 in the measurable state inaccordance with the upper-side supporting points 21A and lower-sidesupporting points 25B.

The shifted state of the complex stack 19 in the measurable state isdescribed specifically taking the shifted state in the upper-side unitregion R1 as an example. A ratio of the degree of deflection e (see FIG.12) in the upper-side unit region R1 to the clearance c (see FIG. 4)between 2 upper-side supporting points 21A located on a diagonal linemaking up the upper-side unit region R1 is preferably 1 down to 0.02%,more preferably 0.5 down to 0.04%.

The pressing force against the circuit board 1 to be inspected in themeasurable state is set to, for example, 110 to 250 kgf.

In this measurable state, all the upper-side electrodes 2 to beinspected on the circuit board 1 to be inspected are, respectively,electrically connected to their corresponding pairs of inspectionelectrodes each composed of the electrode 32A for current supply and theelectrode 32B for voltage measurement in the upper-side adaptor 31through the anisotropically conductive sheet 33, and the terminalelectrodes 32C of this upper-side adaptor 31 are, respectively,electrically connected to their corresponding inspection pins 36 of theupper-side inspection head 35 through the conductive path-forming parts37A of the anisotropically conductive sheet 37.

On the other hand, all the lower-side electrodes 3 to be inspected onthe circuit board 1 to be inspected are, respectively, electricallyconnected to their corresponding pairs of inspection electrodes eachcomposed of the electrode 52A for current supply and the electrode 52Bfor voltage measurement in the lower-side adaptor 51 through theanisotropically conductive sheet 53, and the terminal electrodes 52C ofthis lower-side adaptor 51 are electrically connected to theircorresponding inspection pins 56 of the lower-side inspection head 55through the conductive path-forming parts of the anisotropicallyconductive sheet 57.

A current is supplied between the electrodes for current supply from thetester, and a voltage signal between the electrodes for voltagemeasurement is detected and processed by the tester, whereby electricresistance in the upper-side electrodes 2 to be inspected and lower-sideelectrodes 3 to be inspected can be measured.

According to the above-described first inspection apparatus 10, in themeasurable state, points of application of the pressing force by theupper-side supports 22 and points of application of the pressing forceby the lower-side supports 26 are formed in the form of a lattice atpositions different from one another on the specific plane Ml ofprojection, and the complex stack 19, in which the circuit board 1 to beinspected is compressed, is, as it were, forcedly deformed together withthe upper-side base plate 21 and lower-side base plate 25 in accordancewith the upper-side supporting points 21A and lower-side supportingpoints 25B forming the points of application so as to form a regularwave shape, thereby inhibiting the pressing force from concentrating onthe points of application. As a result, since the pressure distributionin the circuit board 1 to be inspected is uniformed, a state that allthe electrodes (upper-side electrodes 2 to be inspected and lower-sideelectrodes 3 to be inspected) to be inspected in the circuit board 1 tobe inspected have been evenly electrically connected to theircorresponding electrodes for current supply and electrodes for voltagemeasurement can be attained, so that the electric resistance of thecircuit board can be measured with high accuracy.

Since both upper-side base plate 21 and lower-side base plate 25 arepreferably made thinner for the purpose of achieving such a state, theweight of the whole first inspection apparatus 10 is made light by thereduction of mass of each of the upper-side base plate 21 and lower-sidebase plate 25. The mass of each of the upper-side base plate 21 andlower-side base plate 25 is actually reduced to at most half of the massof base plates constructing the conventional inspection apparatus forcircuit board.

Accordingly, according to the first inspection apparatus 10, thethickness of the anisotropically conductive sheets can be made thinwithout involving defectiveness, so that the electrical inspection of acircuit board can be conducted with high reliability even when thecircuit board has inspection object electrodes small in size and pitchor clearance, and moreover the weight saving of the apparatus itself canbe planed.

Since the pressure distribution in the circuit board 1 to be inspectedis uniformed, those having the construction that conductive particlesare contained in the whole region of a base material composed of anelastic polymeric substance having insulating property in a state evenlyoriented can be suitably used as the anisotropically conductive sheets33, 35 making up each of the upper-side adaptor 31 and lower-sideadaptor 51.

Further, since the measurable state is created by deforming the complexstack 19 together with the upper-side base plate 21 and lower-side baseplate 25, it is not necessary to use those, the respective overalllengths of which have been equalized with high precision, as theplurality of the upper-side supports 22 and lower-side supports 26 forforming the upper-side supporting points 21A and lower-side supportingpoints 25B, which are points of application, on each of the upper-sidebase plate 21 and lower-side base plate 25 so far as the inspectionapparatus has the construction that this measurable state can beattained. As a result, the first inspection apparatus 10 can be easilyproduced.

Since the conduction between each of the inspection object electrodes(upper-side electrodes 2 to be inspected and upper-side electrodes 3 tobe inspected) in the circuit board 1 to be inspected and pair ofinspection electrodes can be achieved by small pressing force to bringabout the measurable state, durable strength in pressurization requiredof the component members can be made low. As a result, membersrelatively low in durable strength in pressurization can be used as thecomponent members of the first inspection apparatus 10, whereby theminiaturization and simplification of the inspection apparatus itselfcan be expected, and production cost can be reduced.

Since the electrical inspection of the circuit board 1 to be inspectedcan be conducted by small pressing force, the deterioration of theanisotropically conductive sheets 33, 37, 53 and 57 caused by repetitivepressurization in every inspection can be inhibited. Accordingly, thefrequency of replacement of the anisotropically conductive sheets 33,37, 53 and 57 in the first inspection apparatus 10 can be lessened, sothat high inspection efficiency can be achieved, and inspection cost canbe reduced.

Further, thin plates are used as the upper-side base plate 21 andlower-side base plate 25, whereby each of the through-holes(specifically, through-holes 21B and 25D for inspection pins, andthrough-holes 25C for positioning pin) required upon construction can beformed by one drilling operation. Accordingly, the time required for thedrilling operation can be shortened, and the rate of success in drillingoperation becomes high compared with an inspection apparatus equippedwith thick base plates that require plural times of drilling operationfor forming a through-hole, so that the through-holes can be formed withhigh efficiency to attain high productivity.

FIG. 13 is a cross-sectional view illustrating, on an enlarged scale, apart of the construction of another exemplary inspection apparatus forcircuit board according to the present invention.

This inspection apparatus (hereinafter also referred to as “secondinspection apparatus”) is used for conducting electrical inspection of acircuit board, on both surfaces of which inspection object electrodes(electrodes to be inspected) have been formed. In this inspectionapparatus, an upper-side board-compressing member 60 arranged on anupper side of an inspection object circuit board (circuit board to beinspected) 1 and having a plurality of inspection electrodes 62A formedin accordance with a pattern corresponding to upper-side electrodes 2 tobe inspected of the circuit board 1 to be inspected and provided with ananisotropically conductive sheet 33 on its front surface (lower surfacein FIG. 13) and, a lower-side board-compressing member 65 arranged on alower side of the circuit board 1 to be inspected and having a pluralityof inspection electrodes 67A formed in accordance with a patterncorresponding to lower-side electrodes 3 to be inspected of the circuitboard 1 to be inspected and provided with an anisotropically conductivesheet 53 on its front surface (upper surface in FIG. 13) are arranged soas to be vertically opposed to each other.

The second inspection apparatus has the same construction as the firstinspection apparatus 10 except that the construction of the upper-sideboard-compressing member and lower-side board-compressing member isdifferent, and as the first inspection apparatus 10, the secondinspection apparatus takes circuit boards having flexibility as theobject of inspection. In FIG. 13, the same reference numerals as in thefirst inspection apparatus are given to component members having thesame construction as in the first inspection apparatus.

In this embodiment, the second inspection apparatus takes circuit boardshaving the same construction as the inspection object circuit boardrelated to the first inspection apparatus, as the object of inspection.

Even in the second inspection apparatus, as with the first inspectionapparatus 10, an upper-side supporting points formed on an upper-sidebase plate 21, on which the upper-side board-compressing member 60 isprovided, and a lower-side supporting point formed on a lower-side baseplate 25, on which the lower-side board-compressing member 65 isprovided, are arranged at positions different from each other on a plane(specific plane of projection) of projection in a thickness-wisedirection of the upper-side board-compressing member 60 and lower-sideboard-compressing member 65 when the second inspection apparatus is seenthrough from above (from above in FIG. 13).

Specifically, the upper-side supporting points and the lower-sidesupporting points are formed in the form of a lattice on the upper-sidebase plate 21 and on the lower-side base plate 25, respectively.

When the supporting points are formed in the form of a lattice in such amanner, a clearance between upper-side supporting points adjacent toeach other and a clearance between lower-side supporting points adjacentto each other are each preferably 10 to 100 mm, more preferably 12 to 70mm, particularly preferably 15 to 50 mm.

In the second inspection apparatus, the upper-side board-compressingmember 60 is constructed by arranging an upper-side adaptor 61 composedof a circuit board 62 for inspection and an anisotropically conductivesheet 33, and an upper-side inspection head 63 composed of inspectionpins 36 fixed by the upper-side base plate 21 and a spacer board 38 andan anisotropically conductive sheet 64 in this order from below in FIG.13.

The circuit board 62 for inspection making up the upper-side adaptor 61in the upper-side board-compressing member 60 has the construction thatthe inspection electrodes 62A formed in accordance with a patterncorresponding to the upper-side electrodes 2 to be inspected of thecircuit board 1 to be inspected are provided on its front surface, and aplurality of terminal electrodes 62B are arranged on its back surface(upper surface in FIG. 13) according to positions of lattice pointshaving a pitch of, for example, 0.2 mm, 0.3 mm, 0.45 mm, 0.5 mm, 0.75mm, 0.8 mm, 1.06 mm, 1.27 mm, 1.5 mm, 1.8 mm or 2.54 mm.

Each of the terminal electrodes 62B in the circuit board 62 forinspection is electrically connected to its corresponding inspectionelectrode 62A through an internal wiring part 62C.

The anisotropically conductive sheet 64 making up the upper-sideinspection head 64 in the upper-side board-compressing member 60 is theso-called dispersion type anisotropically conductive sheet thatconductive particles are contained in a base material composed of anelastic polymeric substance having insulating property in a stateoriented so as to align in a thickness-wise direction of theanisotropically conductive sheet 64, and has the construction thatconductive paths are formed by chains of the conductive particles whenthe sheet is pressurized in the thickness-wise direction in themeasurable state. This anisotropically conductive sheet 64 is fixed by aproper means.

The anisotropically conductive sheet 64 preferably has a thickness of0.1 to 1.5 mm and can be obtained by using the above-describedsheet-forming material in accordance with the above-described productionprocess.

The upper-side board-compressing member 60 of the above-describedconstruction can be produced by arranging the spacer board 38, in whicha plurality of through-holes for inspection pin have been formed, theanisotropically conductive sheet 64, the circuit board 62 for inspectionand the anisotropically conductive sheet 33 at prescribed positions inthis order on the front surface of the upper-side base plate 21 in whichthe inspection pins 36 have been infixed.

In the second inspection apparatus, the lower-side board-compressingmember 65 is constructed by arranging a lower-side adaptor 66 composedof a circuit board 67 for inspection and an anisotropically conductivesheet 53, and a lower-side inspection head 68 composed of inspectionpins 56 fixed by the lower-side base plate 25 and a spacer board 58 andan anisotropically conductive sheet 69 in this order from above in FIG.13.

The circuit board 67 for inspection making up the lower-side adaptor 66in the lower-side board-compressing member 65 has the construction thatthe inspection electrodes 67A formed in accordance with a patterncorresponding to the lower-side electrodes 3 to be inspected of thecircuit board 1 to be inspected are provided on its front surface, and aplurality of terminal electrodes 67B are arranged on its back surface(lower surface in FIG. 13) according to positions of lattice pointshaving a pitch of, for example, 0.2 mm, 0.3 mm, 0.45 mm, 0.5 mm, 0.75mm, 0.8 mm, 1.06 mm, 1.27 mm, 1.5 mm, 1.8 mm or 2.54 mm.

Each of the terminal electrodes 67B in the circuit board 67 forinspection is electrically connected to inspection electrode 67A throughan internal wiring part 67C.

The anisotropically conductive sheet 69 making up the lower-sideinspection head 68 in the lower-side board-compressing member 65 is theso-called dispersion type anisotropically conductive sheet thatconductive particles are contained in a base material composed of anelastic polymeric substance having insulating property in a stateoriented so as to align in a thickness-wise direction of theanisotropically conductive sheet 69, and has the construction thatconductive paths are formed by chains of the conductive particles whenthe sheet is pressurized in the thickness-wise direction in themeasurable state. This anisotropically conductive sheet 69 is fixed by aproper means.

The anisotropically conductive sheet 69 preferably has a thickness of0.1 to 1.5 mm and can be obtained by using the above-describedsheet-forming material in accordance with the above-described productionprocess.

The lower-side board-compressing member 65 of the above-describedconstruction can be produced by arranging an alignment movable plate 15,in which a substantially rectangular hole 15A has been formed, thespacer board 58, in which a plurality of through-holes for inspectionpin have been formed, the anisotropically conductive sheet 69, thecircuit board 67 for inspection and the anisotropically conductive sheet53 at prescribed positions in this order on the front surface of thelower-side base plate 25 in which the inspection pins 56 have beeninfixed at its projected part 25A.

In the second inspection apparatus of the above-described construction,as the first inspection apparatus 10, the circuit board 1 to beinspected is compressed by the upper-side board-compressing member 60and lower-side board-compressing member 65, a complex stack composed ofthe circuit board 1 to be inspected, and the upper-sideboard-compressing member 60 and lower-side board-compressing member 65compressing the circuit board, is deflected by shifting in thethickness-wise direction together with the upper-side base plate 21 andlower-side base plate 25, at positions where the stack is respectivelypressed by the upper-side supports and lower-side supports in accordancewith the upper-side supporting points and lower-side supporting points,and deformed in the form of a regular wave to bring about a measurablestate.

In such a measurable state, a gap between upper-side and low-sidesupports in the thickness-wise direction of the complex stack between anupper-side level of the upper-side support and a lower-side level of thelower-side support becomes smaller than the total thickness of thecomplex stack, the upper-side base plate 21 and the lower-side baseplate 25.

As an example of the shifted state of the complex stack in themeasurable state of this second inspection apparatus, a ratio of thedegree b of deflection in the upper-side unit region to the clearancebetween 2 upper-side supporting points located on a diagonal line makingup the upper-side unit region is preferably 1 down to 0.02%, morepreferably 0.5 down to 0.04% in the same manner as the example of theshifted state related to the first inspection apparatus 10.

The pressing force against the circuit board 1 to be inspected in themeasurable state is set to, for example, 110 to 250 kgf.

In this measurable state, all the upper-side electrodes 2 to beinspected on the circuit board 1 to be inspected, respectively, areelectrically connected to their corresponding inspection electrodes 62Aof the upper-side adaptor 61 through the anisotropically conductivesheet 33, and the terminal electrodes 62B of this upper-side adaptor 61are, respectively, electrically connected to their correspondinginspection pins 36 of the upper-side inspection head 63 through theanisotropically conductive sheet 64. On the other hand, all thelower-side electrodes 3 to be inspected on the circuit board 1 to beinspected are, respectively, electrically connected to theircorresponding inspection electrodes 67A of the lower-side adaptor 66through the anisotropically conductive sheet 53, and the terminalelectrodes 67B of this lower-side adaptor 66 are, respectively,electrically connected to their corresponding inspection pins 56 of thelower-side inspection head 68 through the anisotropically conductivesheet 69.

In such a manner, the upper-side electrodes 2 to be inspected andlower-side electrodes 3 to be inspected of the circuit board 1 to beinspected are electrically connected to their corresponding inspectionpins 36 in the upper-side inspection head 63 and their correspondinginspection pins 56 in the lower-side inspection head 68, respectively,whereby a state that they have been electrically connected to aninspection circuit of a tester is achieved and necessary electricalinspection is conducted in this state.

According to the above-described second inspection apparatus, in themeasurable state, points of application of the pressing force by theupper-side supports and points of application of the pressing force bythe lower-side supports are formed in the form of a lattice at positionsdifferent from one another on the specific plane of projection, and thecomplex stack, in which the circuit board 1 to be inspected iscompressed, is, as it were, forcedly deformed together with theupper-side base plate 21 and lower-side base plate 25 in accordance withthe upper-side supporting points and lower-side supporting pointsforming the points of application so as to form a regular wave shape,thereby inhibiting the pressing force from concentrating on the pointsof application. As a result, since the pressure distribution in thecircuit board 1 to be inspected is uniformed, a state that all theelectrodes (upper-side electrodes 2 to be inspected and lower-sideelectrodes 3 to be inspected) to be inspected in the circuit board 1 tobe inspected have been evenly electrically connected to theircorresponding inspection electrodes 62A and 67A can be attained, so thatthe electrical inspection of the circuit board can be performed withhigh reliability.

Since both upper-side base plate 21 and lower-side base plate 25 arepreferably made thinner for the purpose of achieving such a state, theweight of the whole second inspection apparatus is made light by thereduction of mass of each of the upper-side base plate 21 and lower-sidebase plate 25. The mass of each of the upper-side base plate 21 andlower-side base plate 25 is actually reduced to at most half of the massof base plates constructing the conventional inspection apparatus forcircuit board.

Accordingly, according to the second inspection apparatus for circuitboard, the thickness of the anisotropically conductive sheets can bemade thin without involving defectiveness in such a manner as in thefirst inspection apparatus 10, so that the electrical inspection of acircuit board can be conducted with high reliability even when thecircuit board has inspection object electrodes small in size and pitchor clearance, and moreover the weight saving of the apparatus itself canbe expected.

Since the pressure distribution in the circuit board 1 to be inspectedis uniformed, anisotropically conductive sheets having the constructionthat conductive particles are contained in the whole region of a basematerial composed of an elastic polymeric substance having insulatingproperty in a state evenly oriented can be suitably used as theanisotropically conductive sheets.

Further, since the measurable state is created by deforming the complexstack together with the upper-side base plate 21 and lower-side baseplate 25, it is not necessary to use those, the respective overalllengths of which have been equalized with high precision, as theplurality of the upper-side supports and lower-side supports for formingthe upper-side supporting points and lower-side supporting points, whichare points of application, on each of the upper-side base plate 21 andlower-side base plate 25 so far as the inspection apparatus has theconstruction that this measurable state can be attained. As a result,the second inspection apparatus can be easily produced.

Since the conduction between each of the inspection object electrodes(upper-side electrodes 2 to be inspected and upper-side electrodes 3 tobe inspected) in the circuit board 1 to be inspected and inspectionelectrodes 62A, 67A can be achieved by small pressing force to bringabout the measurable state, durable strength in pressurization requiredof the component members can be made low. As a result, membersrelatively low in durable strength in pressurization can be used as thecomponent members of the second inspection apparatus, whereby theminiaturization and simplification of the inspection apparatus itselfcan be expected, and production cost can be reduced.

Since the electrical inspection of the circuit board 1 to be inspectedcan be conducted by small pressing force, the deterioration of theanisotropically conductive sheets 33, 64, 53 and 69 caused by repetitivepressurization in every inspection can be inhibited. Accordingly, thefrequency of replacement of the anisotropically conductive sheets 33,64, 53 and 69 in the second inspection apparatus can be lessened, sothat high inspection efficiency can be achieved, and inspection cost canbe reduced.

Further, thin plates are used as the upper-side base plate 21 andlower-side base plate 25, whereby each of the through-holes required forthe construction can be formed by one drilling operation. Accordingly,the time required upon drilling operation can be shortened, and the rateof success in drilling operation becomes high compared with aninspection apparatus equipped with thick base plates that require pluraltimes of drilling operation for forming a through-hole, so that thethrough-holes can be formed with high efficiency to attain highproductivity.

Although the present invention has been described specifically above,the present invention is not limited to the above-described embodiments,and various modifications can be added thereto.

For example, the inspection apparatus for circuit board may be such thatan upper-side inspection head 71 and a lower-side inspection head 75,which are provided on plate-like upper-side base plate 74 and lower-sidebase plate 78, respectively, are respectively constructed by plate-likeelectrode devices 72 and 76 and anisotropically conductive sheets 73 and77 fixed and arranged on respective front surfaces (surfaces positionedon the side of the circuit board 1 to be inspected in FIG. 14) of theelectrode devices 72, 76 as illustrated in FIG. 14. Each of theelectrode devices 72 and 76 has a plurality of connecting electrodes(not illustrated) arranged at positions of lattice points having thesame pitch as the terminal electrodes (not illustrated) of theupper-side adaptor 31 and the lower-side adaptor 51 on its frontsurface. Each of these connecting electrodes is electrically connectedto connectors (not illustrated) respectively provided on the upper-sidesupport-infixing plate 23 and the lower-side support-infixing plate 27by a wire (not illustrated) through an electrode pin (not illustrated)and further electrically connected to a tester (not illustrated) throughthe connectors. In FIG. 14, reference numeral 79 designates a spacer forfixing the positioning pin 13 making up the circuit board-holdingmechanism, and the same reference numerals as in the first inspectionapparatus 10 illustrated in FIG. 1 are given to component members havingthe same construction as those in the first inspection apparatus amongcomponent elements in the inspection apparatus 70.

The inspection apparatus for circuit board is not limited to thosehaving the construction that the upper-side supporting points andlower-side supporting points are respectively formed so as to beregularly arranged on corresponding base plates and may be those havingthe construction that the upper-side supports and lower-side supportsforming the supporting points are arranged in an irregular stateaccording to arranged states of other component members such as wires.

In the inspection apparatus for circuit board, those of the dispersiontype or uneven distribution type may be suitably used as theanisotropically conductive sheets making up the inspection apparatus.Further, those having an irregular surface with conductive path-formingparts projected on one side or both sides thereof or those having noirregularities may be suitably used as the uneven distribution typeanisotropically conductive sheet.

EXAMPLES

The present invention will hereinafter be described specifically by thefollowing Examples. However, the present invention is not limited tothese Examples.

Example 1

An inspection apparatus (hereinafter also referred to as “InspectionApparatus (1)”) for circuit board of the following conditions, which isadapted to an inspection section of a rail-carried type automaticcircuit board inspection machine “STARREC V5” (manufactured byNIDEC-READ CORPORATION) was produced in accordance with the constructionshown in FIG. 1.

Upon the production of this Inspection Apparatus (1), that having athickness of 4.0 mm was used as an upper-side base plate, so that onethrough-hole was capable of being formed by one drilling operation, thedrilling operation time required to form one through-hole was able to beshortened compared with a lower-side base plate that has a thickness of6.0 mm and requires plural times of drilling operation for forming onethrough-hole, and the through-holes were capable of being formed withhigh efficiency.

In Inspection Apparatus (1), as illustrated in FIG. 4, upper-sidesupporting points and lower-side supporting points are respectivelyformed in the form of a lattice and arranged in such a manner that onthe specific plane M1 of projection, one lower-side supporting point 25Bis arranged at a position where 2 diagonal lines intersect with eachother within a rectangular upper-side unit region R1 partitioned byadjacent 4 upper-side supporting points 21A, and one upper-sidesupporting point 21A is arranged at a position where 2 diagonal linesintersect with each other within a rectangular lower-side unit region R2partitioned by adjacent 4 lower-side supporting points 25B.

(1) Upper-Side Adaptor:

[Circuit Board for Inspection]

Dimensions of electrodes for current supply:

-   -   0.06 mm by 0.15 mm

Dimensions of electrodes for voltage measurement:

-   -   0.06 mm by 0.15 mm

Clearance between electrode for current supply and electrode for voltagemeasurement: 90 μm

Dimensions of terminal electrodes: 0.4 mm in diameter

Material of base material:

-   -   glass fiber-reinforced epoxy resin

Maximum thickness: 1.0 mm

[Anisotropically Conductive Sheet]

Dimensions: 110 mm by 110 mm by 0.1 mm in thickness

Conductive particles:

-   -   material: nickel particles plated with gold,    -   average particle diameter: 20 μm,    -   content: 18% by volume

Elastic polymeric substance:

-   -   Material: silicone rubber,    -   hardness: 40

Electric resistance in thickness-wise direction in measurable state: 0.1Ω

Ratio of electric resistance value in thickness-wise direction toelectric resistance value in plane direction: 1,000 or higher

(2) Upper-Side Inspection Head:

[Inspection Pin]

Material: brass plated with gold

Dimensions of tip part:

-   -   0.35 mm in outer diameter, 0.1 mm in overall-length

Dimensions of central part:

-   -   0.48 mm in outer diameter, 1.8 mm in overall length

Dimensions of large-diameter part:

-   -   0.55 mm in outer diameter, 0.1 mm in overall length

Dimensions of proximal part:

-   -   0.48 mm in outer diameter, 3.0 mm in overall length

Clearance between adjacent inspection pins: 0.75 mm

[Anisotropically Conductive Sheet]

Dimensions: 110 mm by 110 mm

Thickness of conductive path-forming parts: 0.6 mm

Outer diameter of conductive path-forming parts:

-   -   0.25 mm

Projected height of conductive path-forming parts:

-   -   0.05 mm

Conductive particles:

-   -   material: nickel particles plated with gold, average particle        diameter: 35 μm,    -   content: 13% by volume

Elastic polymeric substance:

-   -   material: silicone rubber,    -   hardness: 30        [Spacer Board]

Material: glass fiber-reinforced epoxy resin material “FR-4”

Dimensions: 200 mm by 346 mm by 1.9 mm in thickness

(3) Upper-Side Base Plate:

Material: glass fiber-reinforced epoxy resin material “FR-4”

Dimensions: 200 mm by 346 mm by 4.0 mm in thickness

Mass: 0.5 kg

(4) Upper-Side Support:

Material: brass

Dimensions:

-   -   outer diameter of tip part: 4 mm,    -   overall length: 67 mm

Clearance between adjacent upper-side supports:

-   -   Lateral direction in FIG. 1 (hereinafter also referred to as        “lateral direction” merely): 32.25 mm,    -   Direction (hereinafter also referred to as “vertical direction”        merely) perpendicular to lateral direction: 24.75 mm        (5) Lower-Side Adaptor        [Circuit Board for Inspection]

Dimensions of electrodes for current supply:

-   -   0.06 mm by 0.15 mm

Dimensions of electrodes for voltage measurement:

-   -   0.06 mm by 0.15 mm

Clearance between electrode for current supply and electrode for voltagemeasurement: 90 μm

Dimensions of terminal electrodes: 0.4 mm in diameter

Material of base material:

-   -   glass fiber-reinforced epoxy resin

Maximum thickness: 1.0 mm

[Anisotropically Conductive Sheet]

Dimensions: 100 mm by 110 mm by 0.1 mm in thickness

Conductive particles:

-   -   material: nickel particles plated with gold,    -   average particle diameter: 20 μm,    -   content: 18% by volume

Elastic polymeric substance:

-   -   material: silicone rubber,    -   hardness: 40

Electric resistance in thickness-wise direction in measurable state: 0.1Ω

Ratio of electric resistance value in thickness-wise direction toelectric resistance value in plane direction: 1,000 or higher

(6) Lower-Side Inspection Head:

[Inspection Pin]

Material: brass plated with gold

Dimensions of tip part:

-   -   0.35 mm in outer diameter, 0.1 mm in overall length

Dimensions of large-diameter part:

-   -   0.55 mm in outer diameter, 1.8 mm in overall length

Dimensions of proximal part:

-   -   0.48 mm in outer diameter, 3.0 mm in overall length

Clearance between adjacent inspection pins: 0.75 mm

[Anisotropically Conductive Sheet]

Dimensions: 100 mm by 110 mm

Thickness of conductive path-forming parts: 0.6 mm

Outer diameter of conductive path-forming parts:

-   -   0.25 mm

Projected height of conductive path-forming parts:

-   -   0.05 mm

Conductive particles:

-   -   material: nickel particles plated with gold,    -   average particle diameter: 35 μm,    -   content: 13% by volume

Elastic polymeric substance:

-   -   material: silicone rubber,    -   hardness: 30        [Spacer Board]

Material: glass fiber-reinforced epoxy resin material “FR-4”

Dimensions: 100 mm by 338 mm by 1.9 mm in thickness

[Alignment movable plate]

Dimensions: 100 mm by 338 mm by 2.95 mm in thickness

(7) Lower-Side Base Plate:

Material: glass fiber-reinforced epoxy resin material “FR-4”

Dimensions: 100 mm by 338 mm by 6.0 mm in thickness

Projected height of projected part: 3.0 mm

Mass: 0.4 kg

(8) Lower-Side Support:

Material: brass

Dimensions:

-   -   outer diameter of tip part: 4 mm,    -   overall length: 65 mm

Clearance between adjacent lower-side supports:

-   -   Lateral direction: 32.25 mm,    -   Vertical direction: 24.75 mm        (9) Upper-Side Supporting Points and Lower-Side Supporting        Points:

Clearance between adjacent upper-side supporting points:

-   -   Lateral direction: 32.25 mm,    -   Vertical direction: 24.75 mm

Length (clearance c in FIG. 4) of diagonal line in upper-side unitregion: about 41 mm

Clearance between adjacent lower-side supporting points:

-   -   Lateral direction: 32.25 mm,    -   Vertical direction: 24.75 mm

Length of diagonal line in lower-side unit region:

-   -   about 41 mm

Clearance (d in FIG. 4) between lower-side supporting point andupper-side supporting point located within upper-side unit region: about20 mm

In Inspection Apparatus (1), a non-defective circuit board having thefollowing specification was used as a circuit board to be inspected toconduct performance tests (measurement of minimum pressing pressure anddetermination of durability of anisotropically conductive sheets) inaccordance with the following respective methods. The measured resultsof the minimum pressing pressure are shown in Table 1, and thedetermined results of the durability of anisotropically conductivesheets are shown in Table 2.

In the performance tests, it was confirmed that the measurable state ofInspection Apparatus (1) is achieved by deflecting and deforming acomplex stack composed of the non-defective circuit board, and theupper-side board-compressing member and lower-side board-compressingmember for compressing the non-defective circuit board in the form of aregular wave by shifting in the thickness-wise direction together withthe upper-side base plate and lower-side base plate, at positions whereit is respectively pressed by the upper-side supports and lower-sidesupports in accordance with the upper-side supporting points andlower-side supporting points.

[Specification of Non-Defective Circuit Board]

Dimensions: 100 mm by 100 mm by 0.8 mm in thickness

Upper-side electrodes to be inspected:

-   -   Minimum electrode size: 0.3 mm in diameter,    -   Arrangement pitch: 0.75 mm,    -   Number of electrodes: 7,312

Lower-side electrodes to be inspected:

-   -   Minimum electrode size: 0.3 mm in diameter,    -   Arrangement pitch: 0.75 mm,    -   Number of electrodes: 3,784

[Performance Test]

(1) Measurement of Minimum Pressing Pressure:

The Inspection Apparatus (1) produced was installed in an inspectionsection of a rail-carried type automatic circuit board inspectionmachine “STARREC V5”, and the non-defective circuit board provided wasthen set in Inspection Apparatus (1). The pressing pressure of therail-carried type automatic circuit board inspection machine “STARRECV5” was changed stepwise within a range of 100 to 250 kgf, and aconduction resistance value as to the electrodes to be inspected of thenon-defective circuit board when a current of 1 mA was applied to theelectrode for current supply in each pair of inspection electrodes wasmeasured by the electrode for voltage measurement for 10 times everypressing pressure conditions.

An inspection point (hereinafter referred to as “NG inspection point”)at which the conduction resistance value measured reached 100 Ω orhigher was judged to be defective conduction to calculate out aproportion (hereinafter referred to as “proportion of NG inspectionpoints”) of the number of the NG inspection points to the total numberof inspection points. The lowest pressing pressure under which theproportion of NG inspection points was 0.01% or lower was regarded as aminimum pressing pressure.

In the measurement of this conduction resistance value, the pressingpressure related to this measurement was released after completion ofthe measurement of a conduction resistance value to return theinspection apparatus to a non-pressurized state, and a pressing pressureof the prescribed intensity was applied again when the next measurementof a conduction resistance value was conducted.

Since the number of the upper-side electrodes to be inspected in thenon-defective circuit board is 7,312, the number of the lower-sideelectrodes to be inspected is 3,784, and the measurement is conducted 10times every pressing pressure conditions, “the proportion of NGinspection points” specifically indicates a proportion of the NGinspection points to the inspection points of 110,960 calculated out byan equation (7,312+3,784)×10 =110,960 (the same shall applyhereinafter).

In an inspection apparatus, it is necessary that the proportion of NGinspection points is at most 0.01% from the viewpoint of practical use.If the proportion of NG inspection points exceeds 0.01%, an erroneousinspection result that a non-defective circuit board to be inspected isjudged to be a defective may be brought about in some cases. There isthus a possibility that the electrical inspection of circuit boards maynot be conducted with high reliability.

An inspection apparatus is capable of conducting the electricalinspection of circuit boards to be inspected with lower pressing force,as the minimum pressing pressure becomes lower. If the pressing forceupon the inspection can be set low in an inspection apparatus, thedeterioration of circuit boards to be inspected, and component memberssuch as anisotropically conductive sheets and circuit boards forinspection by the pressing force upon the inspection can be inhibited,and parts low in durable strength in pressurization may be used as thecomponent members of the inspection apparatus, so that theminiaturization and simplification of the inspection apparatus can beexpected. As a result, improvement in the durability of the inspectionapparatus itself and reduction in the production cost of the inspectionapparatus can be achieved.

(2) Determination of Durability of Anisotropically Conductive Sheet:

The Inspection Apparatus (1) produced was installed in an inspectionsection of a rail-carried type automatic circuit board inspectionmachine “STARREC V5”, and the non-defective circuit board provided wasthen set in Inspection Apparatus (1). After pressurization was conductedprescribed times against the non-defective circuit board underconditions of a pressing pressure of 130 kgf by the rail-carried typeautomatic circuit board inspection machine “STARREC V5”, a conductionresistance value as to electrodes to be inspected of the non-defectivecircuit board when a current of 1 mA was applied to the electrode forcurrent supply in each pair of inspection electrodes was measured 10times in total by the electrode for voltage measurement under conditionsof a pressing pressure of 130 kgf. An inspection point (NG inspectionpoint) at which the conduction resistance value measured reached 100 Ωor higher was judged to be defective conduction to calculate out aproportion (proportion of NG inspection points) of the number of the NGinspection points to the total number of inspection points.

Pressurization was then conducted prescribed times against thenon-defective circuit board under the same conditions as described aboveexcept that the anisotropically conductive sheets in InspectionApparatus (1) were replaced by new ones, and the pressing pressureconditions were changed to 150 kgf, and thereafter, a proportion of theNG inspection points was then calculated out in the same manner asdescribed above except that the pressing pressure conditions werechanged to 150 kgf to measure a conduction resistance value.

In the measurement of this conduction resistance value related to thedurability of the anisotropically conductive sheets, the pressingpressure related to this measurement was released after completion ofthe measurement of a conduction resistance value to return theinspection apparatus to a non-pressurized state, and a pressing pressureof the prescribed intensity was applied again when the next measurementof a conduction resistance value was conducted.

Comparative Example 1

An inspection apparatus (hereinafter also referred to as “ComparativeInspection Apparatus (1)”) for circuit board having the sameconstruction as Inspection Apparatus (1) except that the thickness ofthe upper-side base plate was set to 10.0 mm, the thickness of thelower-side base plate was set to 13.0 mm, the outer diameter of the tippart of each of the upper-side supports and lower-side supports was setto 6.0 mm, the clearances in the lateral direction between upper-sidesupports and between lower-side supports were each set to 32.25 mm, theclearances in the vertical direction were each set to 24.75 mm, and theupper-side supporting points and lower-side supporting points werearranged in the following manner was produced.

Since those having a greater thickness compared with InspectionApparatus (1) were used as the upper-side base plate and lower-side baseplate in this Comparative Inspection Apparatus (1), the formation of onethrough-hole required plural times of drilling operation, the drillingoperation time required to form one through-hole became long, and so theproductivity was lowered compared with Inspection Apparatus (1).

A minimum pressing pressure and durability of anisotropically conductivesheets were determined in the same manner as in Example 1 except thatComparative Circuit Board (1) produced was used. The measured results ofthe minimum pressing pressure are shown in Table 1, and the determinedresults of the durability of anisotropically conductive sheets are shownin Table 2.

In Comparative Circuit Board (1), the upper-side supporting points andlower-side supporting points are respectively formed in the form of alattice and are arranged in such a manner that as illustrated in FIG.17, an upper-side supporting point 97A and a lower-side supporting point97B are located at the same position on a plane of projection whenComparative Circuit Board (1) is seen through from above. In FIG. 17,one common unit region R4 formed by the upper-side supporting points 97Aand the lower-side supporting points 97B is surrounded by an alternatelong and two short dashes line.

In Comparative Circuit Board (1), the clearance distances betweenadjacent upper-side supporting points and between adjacent lower-sidesupporting points were each 32.25 mm in the lateral direction and 24.75mm in the vertical direction, and the lengths of a diagonal line of theupper-side unit region (clearance c in FIG. 17) and a diagonal line ofthe lower-side unit region are each 41 mm. Incidentally, the clearance dshown in FIG. 4 is 0 mm in Comparative Circuit Board (1). TABLE 1 Mini-mum Pressing Proportion of NG Pressing Pressure Inspection Points (%)Pressure (kgf) 100 110 120 130 150 180 250 (kgf) Example 0.02 0 0 0 0 00 110 Comparative 1.5 0.05 0.02 0 0 0 0 130 Example 1

TABLE 2 Proportion of NG Inspection Points (%) Number of Pressing(count) 1 1000 5000 10000 30000 Example 1 Pressing 130 kgf 0 0 0 0 0.01Pressure Pressing 150 kgf 0 0 0 0 0 Pressure Comparative Pressing 130kgf 0 0 0.7 3.2 — Example 1 Pressure Pressing 150 kgf 0 0 0.15 2.5 —Pressure

Example 2

An inspection apparatus (hereinafter also referred to as “InspectionApparatus (2)”) for circuit board of the following conditions, which isadapted to an inspection section of a rail-carried type automaticcircuit board inspection machine “STARREC V5” (manufactured byNIDEC-READ CORPORATION) was produced in accordance with the constructionshown in FIG. 13.

Upon the production of this Inspection Apparatus (2), that having athickness of 4.0 mm was used as an upper-side base plate, so that onethrough-hole was capable of being formed by one drilling operation, thedrilling operation time required to form one through-hole was able to beshortened compared with a lower-side base plate that has a thickness of6.0 mm and requires plural times of drilling operation for forming onethrough-hole, and the through-holes were capable of being formed withhigh efficiency.

In Inspection Apparatus (2), upper-side supporting points and lower-sidesupporting points are respectively formed in the form of a lattice andarranged in such a manner that on the specific plane of projection, onelower-side supporting point is arranged at a position where 2 diagonallines intersect with each other within a rectangular upper-side unitregion partitioned by adjacent 4 upper-side supporting points, and oneupper-side supporting point is arranged at a position where 2 diagonallines intersect with each other within a rectangular lower-side unitregion partitioned by adjacent 4 lower-side supporting points.

(1) Upper-Side Adaptor:

[Circuit Board for Inspection]

Total number of inspection electrodes: 7,312

Dimensions of minimum inspection electrodes:

-   -   60 μm by 150 μm

Total number of terminal electrodes: 3,784

Dimensions of minimum terminal electrodes:

-   -   60 μm by 150 μm

Material of base material:

-   -   glass fiber-reinforced epoxy resin

Maximum thickness: 1.0 mm

[Anisotropically Conductive Sheet]

Dimensions: 110 mm by 110 mm by 0.1 mm in thickness

Conductive particles:

-   -   material: nickel particles plated with gold,    -   average particle diameter: 20 μm,    -   content: 18% by volume

Elastic polymeric substance:

-   -   material: silicone rubber,    -   hardness: 40        (2) Upper-Side Inspection Head:        [Inspection pin]

Material: brass plated with gold

Dimensions of tip part:

-   -   0.35 mm in outer diameter, 0.1 mm in overall length

Dimensions of central part:

-   -   0.48 mm in outer diameter, 1.8 mm in overall length

Dimensions of large-diameter part:

-   -   0.55 mm in outer diameter, 0.1 mm in overall length

Dimensions of proximal part:

-   -   0.48 mm in outer diameter, 3.0 mm in overall length

Clearance between adjacent inspection pins: 0.75 mm

[Anisotropically Conductive Sheet]

Dimensions: 110 mm by 110 mm by 0.25 mm in thickness

Conductive particles:

-   -   material: nickel particles plated with gold,    -   average particle diameter: 35 μm,    -   content: 13% by volume

Elastic polymeric substance:

-   -   material: silicone rubber,    -   hardness: 30        [Spacer Board]

Material: glass fiber-reinforced epoxy resin material “FR-4”

Dimensions: 200 mm by 346 mm by 1.9 mm in thickness

(3) Upper-Side Base Plate:

Material: glass fiber-reinforced epoxy resin material “FR-4”

Dimensions: 200 mm by 346 mm by 4.0 mm in thickness

Mass: 0.5 kg

(4) Upper-Side Support:

Material: brass

Dimensions:

-   -   outer diameter of tip part: 4 mm,    -   overall length: 67 mm

Clearance between adjacent upper-side supports:

-   -   lateral direction: 32.25 mm    -   vertical direction: 24.75 mm        (5) Lower-Side Adaptor        [Circuit Board for Inspection]

Total number of inspection electrodes: 7,312

Dimensions of minimum inspection electrodes:

-   -   60 μm by 150 μm

Total number of terminal electrodes: 3,784

Dimensions of minimum terminal electrodes:

-   -   60 μm by 150 μm

Material of base material:

-   -   glass fiber-reinforced epoxy resin

Maximum thickness: 1.0 mm

[Anisotropically Conductive Sheet]

Dimensions: 100 mm by 110 mm by 0.1 mm in thickness

Conductive particles:

-   -   material: nickel particles plated with gold,    -   average particle diameter: 20 μm,    -   content: 18% by volume

Elastic polymeric substance:

-   -   material: silicone rubber,    -   hardness: 40        (6) Lower-Side Inspection Head:        [Inspection Pin]

Material: brass plated with gold

Dimensions of tip part:

-   -   0.35 mm in outer diameter, 0.1 mm in overall length

Dimensions of large-diameter part:

-   -   0.55 mm in outer diameter, 1.8 mm in overall length

Dimensions of proximal part:

-   -   0.48 mm in outer diameter, 3.0 mm in overall length

Clearance between adjacent inspection pins: 0.75 mm

[Anisotropically Conductive Sheet]

Dimensions: 100 mm by 110 mm by 0.25 in thickness

Conductive particles:

-   -   material: nickel particles plated with gold,    -   average particle diameter: 35 μm,    -   content: 13% by volume

Elastic polymeric substance:

-   -   material: silicone rubber,    -   hardness: 30        [Spacer Board]

Material: glass fiber-reinforced epoxy resin material “FR-4”

Dimensions: 100 mm by 338 mm by 1.9 mm in thickness

[Alignment Movable Plate]

Dimensions: 100 mm by 338 mm by 2.95 mm in thickness

(7) Lower-Side Base Plate:

Material: glass fiber-reinforced epoxy resin material “FR-4”

Dimensions: 100 mm by 338 mm by 6.0 mm in thickness

Projected height of projected part: 3.0 mm

Mass: 0.4 kg

(8) Lower-Side Support:

Material: brass

Dimensions:

-   -   outer diameter of tip part: 4 mm,    -   overall length: 65 mm

Clearance between adjacent lower-side supports:

-   -   Tateral direction: 32.25 mm,    -   Vertical direction: 24.75 mm        (9) Upper-Side Supporting Points and Lower-Side Supporting        Points:

Clearance between adjacent upper-side supporting points:

-   -   Lateral direction: 32.25 mm,    -   Vertical direction: 24.75 mm

Length of diagonal line in upper-side unit region:

-   -   about 41 mm

Clearance between adjacent lower-side supporting points:

-   -   Lateral direction: 32.25 mm,    -   Vertical direction: 24.75 mm

Length of diagonal line in lower-side unit region: about 41 mm

Clearance between lower-side supporting point and upper-side supportingpoint located within upper-side unit region: about 20 mm

In Inspection Apparatus (2), the non-defective circuit board used inExample 1 was used as a circuit board to be inspected to conduct aperformance test in the same manner as in the measurement of the minimumpressing pressure in Example 1 except that the conduction resistancevalue when a current of 1 mA was applied to an inspection electrode inthe measurement of the minimum pressing pressure in Example 1 wasmeasured in the inspection electrode, and to conduct another performancetest in the same manner as in the determination of the durability of theanisotropically conductive sheets in Example 1 except that theconduction resistance value when a current of 1 mA was applied to aninspection electrode in the determination of the durability of theanisotropically conductive sheets in Example 1 was measured in theinspection electrode, the pressing pressure conditions of 130 kgf waschanged to 150 kgf, and the pressing pressure conditions of 150 kgf waschanged to 180 kgf. The measured results of the minimum pressingpressure are shown in Table 3, and the determined results of thedurability of anisotropically conductive sheets are shown in Table 4.

In the performance tests, it was confirmed that the measurable state ofInspection Apparatus (2) is achieved by deflecting and deforming acomplex stack composed of the non-defective circuit board, and theupper-side board-compressing member and lower-side board-compressingmember for compressing the non-defective circuit board in the form of aregular wave by shifting in the thickness-wise direction together withthe upper-side base plate and lower-side base plate, at positions whereit is respectively pressed by the upper-side supports and lower-sidesupports in accordance with the upper-side supporting points andlower-side supporting points.

Comparative Example 2

An inspection apparatus (hereinafter also referred to as “ComparativeInspection Apparatus (2)”) for circuit board having the sameconstruction as Inspection Apparatus (2) except that the thickness ofthe upper-side base plate was set to 10.0 mm, the thickness of thelower-side base plate was set to 13.0 mm, the outer diameter of the tippart of each of the upper-side supports and lower-side supports was setto 6.0 mm, the clearances in the lateral direction between upper-sidesupports and between lower-side supports were each set to 32.25 mm, andthe clearances in the vertical direction were each set to 24.75 mm wasproduced.

Since those having a greater thickness compared with InspectionApparatus (2) were used as the upper-side base plate and lower-side baseplate in this Comparative Inspection Apparatus (2), the formation of onethrough-hole required plural times of drilling operation, the drillingoperation time required to form one through-hole became long, and so theproductivity was lowered compared with Inspection Apparatus (2).

A minimum pressing pressure and durability of anisotropically conductivesheets were determined in the same manner as in Example 2 except thatComparative Circuit Board (2) produced was used. The measured results ofthe minimum pressing pressure are shown in Table 3, and the determinedresults of the durability of anisotropically conductive sheets are shownin Table 4.

In Comparative Circuit Board (2), the upper-side supporting points andlower-side supporting points are respectively formed in the form of alattice under the same conditions as the upper-side supporting pointsand lower-side supporting points in Comparative Circuit Board (1). TABLE3 Minimum Pressing Proportion of NG Pressing Pressure Inspection Points(%) Pressure (kgf) 100 110 130 150 180 250 (kgf) Example 2 0.01 0 0 0 00 110 Comparative 2.3 0.2 0.03 0 0 0 150 Example 2

TABLE 4 Proportion of NG Inspection Points (%) Number of Pressing(Count) 1 1000 5000 10000 30000 Example 2 Pressing 150 kgf 0 0 0 0 0Pressure Pressing 180 kgf 0 0 0 0 0.02 Pressure Comparative Pressing 150kgf 0 0 0.9 2.3 — Example 2 Pressure Pressing 180 kgf 0 0 0.2 3.1 —Pressure

1. An inspection apparatus for circuit board for conducting electricalinspection of an inspection object circuit board by electricallyconnecting inspection object electrodes of the inspection object circuitboard to a plurality of inspection electrodes formed in accordance witha pattern corresponding to the inspection object electrodes through ananisotropically conductive sheet, which comprises: an upper-sideboard-compressing member arranged on an upper side of the inspectionobject circuit board and a lower-side board-compressing member arrangedon a lower side of the inspection object circuit boards, wherein eitherone of the upper-side board-compressing member and lower-sideboard-compressing member has the plurality of the inspection electrodes,the upper-side board-compressing member and lower-side board-compressingmember are respectively provided on base plates supported by a pluralityof supports infixed into support-infixing plates, and an upper-sidesupporting point corresponds to the upper-side support on the upper-sidebase plate related to the upper-side board-compressing member and alower-side supporting point corresponds to the lower-side support on thelower-side base plate related to the lower-side board-compressing memberare arranged at positions different from each other on a plane ofprojection in a thickness-wise direction of the upper-sideboard-compressing member and lower-side board-compressing member whenthe inspection apparatus is seen through from above.
 2. The inspectionapparatus for circuit board according to claim 1, wherein the upper-sideboard-compressing member has an anisotropically conductive sheet on itssurface, and the lower-side board-compressing member has ananisotropically conductive sheet on its surface.
 3. The inspectionapparatus for circuit board according to claim 1, wherein the upper-sidebase plate and the lower-side base plate are pressed, respectively, bythe upper-side supports and the lower-side supports, thereby bringingabout a measurable state that the inspection object circuit board iscompressed by the upper-side board-compressing member and lower-sideboard-compressing member.
 4. The inspection apparatus for circuit boardaccording to claim 1, wherein, in the measurable state, a complex stackcomposed of the inspection object circuit board, and the upper-sideboard-compressing member and lower-side board-compressing member forcompressing the inspection object circuit board is deformed by shiftingin the thickness-wise direction together with the upper-side base plateand lower-side base plate, at positions, over the whole body,respectively pressed by the upper-side supports and lower-side supportsin accordance with the upper-side supporting points and lower-sidesupporting points.
 5. The inspection apparatus for circuit boardaccording to claim 1, wherein, in the measurable state, a gap in thethickness-wise direction of the complex stack between a tip level in theupper-side support and a tip level in the lower-side support is smallerthan the total thickness of the complex stack, the upper-side base plateand the lower-side base plate.
 6. The inspection apparatus for circuitboard according to claim 1, wherein the upper-side supporting points andthe lower-side supporting points are formed in the form of a lattice onthe upper-side base plate and on the lower-side base plate,respectively, and on the plane of projection in the thickness-wisedirection of the upper-side board-compressing member and the lower-sideboard-compressing member, only one lower-side supporting point isarranged within an upper-side unit region partitioned by adjacent 4upper-side supporting points, and only one upper-side supporting pointis arranged within a lower-side unit region partitioned by adjacent 4lower-side supporting points.
 7. The inspection apparatus for circuitboard according to claim 6, wherein clearances between upper-sidesupporting points adjacent to each other related to the upper-side unitregion, and between lower-side supporting points adjacent to each otherrelated to the lower-side unit region are each 10 to 100 mm.
 8. Theinspection apparatus for circuit board according to claim 1, wherein theupper-side base plate and lower-side base plate are each composed of aninsulating material having a resistivity of at least 1×10¹⁰ Ω·cm, andhave a thickness of 1 to 10 mm.
 9. The inspection apparatus for circuitboard according to claim 1, wherein the thickness of each of theupper-side base plate and lower side base plate is at most 5 mm.
 10. Aninspection process for circuit board, which comprises; using theinspection apparatus for circuit board according to claim 1, pressingthe upper-side base plate and the lower-side base plate by theupper-side supports and the lower-side supports, respectively, to form ameasurable state that an inspection object circuit board is compressedby the upper-side board-compressing member and lower-sideboard-compressing member, and in this measurable state, deforming acomplex stack composed of the inspection object circuit board and theupper-side board-compressing member and lower-side board compressingmember for compressing the inspection object circuit board by shiftingin the thickness-wise direction together with the upper-side base plateand lower-side base plate, at positions, over the whole body,respectively pressed by the upper-side supports and lower-side supportsin accordance with the upper-side supporting points and lower-sidesupporting points.
 11. An inspection apparatus for circuit board formeasuring an electric resistance of an inspection object circuit boardby electrically connecting a pair of inspection electrodes formed of anelectrode for current supply and an electrode for voltage measurementarranged in relation separated from each other to each of a plurality ofinspection object electrodes formed on the inspection object circuitboard, through an anisotropically conductive sheet, which comprises: anupper-side board-compressing member arranged on an upper side of theinspection object circuit board and having an anisotropically conductivesheet on its surface, and a lower-side board-compressing member arrangedon a lower side of the inspection object circuit board and having ananisotropically conductive sheet on its surface, wherein the upper-sideboard-compressing member and lower-side board-compressing member eachhave plural pairs of inspection electrodes and are respectively providedon base plates supported by a plurality of supports infixed intosupport-infixing plates, and an upper-side supporting point correspondsto the upper-side support on the upper-side base plate related to theupper-side board-compressing member and a lower-side supporting pointcorresponds to the lower-side support on the lower-side base platerelated to the lower-side board-compressing member are arranged atpositions different from each other on a plane of projection in athickness-wise direction of the upper-side board-compressing member andlower-side board-compressing member when the inspection apparatus isseen through from above.
 12. The inspection apparatus for circuit boardaccording to claim 11, wherein the upper-side base plate and thelower-side base plate are pressed, respectively, by the upper-sidesupports and the lower-side supports, thereby bringing about ameasurable state that the inspection object circuit board is compressedby the upper-side board-compressing member and lower-sideboard-compressing member to carry out the measurement of the electricresistance.
 13. The inspection apparatus for circuit board according toclaim 11, wherein, in the measurable state, a complex stack composed ofthe inspection object circuit board, and the upper-sideboard-compressing member and lower-side board-compressing member forcompressing the inspection object circuit board is deformed by shiftingin the thickness-wise direction together with the upper-side base plateand lower-side base plate, at positions, over the whole body,respectively pressed by the upper-side supports and lower-side supportsin accordance with the upper-side supporting points and lower-sidesupporting points.
 14. The inspection apparatus for circuit boardaccording to claim 11, wherein, in the measurable state, a gap in thethickness-wise direction of the complex stack between a tip level in theupper-side support and a tip level in the lower-side support is smallerthan the total thickness of the complex stack, the upper-side base plateand the lower-side base plate.
 15. The inspection apparatus for circuitboard according to claim 11, wherein the thickness of each of theupper-side base plate and lower side base plate is at most 5 mm.
 16. Theinspection apparatus for circuit board according to claim 11, whereinthe upper-side supporting points and the lower-side supporting pointsare formed in the form of a lattice on the upper-side base plate and onthe lower-side base plate, respectively, and on the plane of projectionin the thickness-wise direction of the upper-side board-compressingmember and the lower-side board-compressing member, only one lower-sidesupporting point is arranged within an upper-side unit regionpartitioned by adjacent 4 upper-side supporting points, and only oneupper-side supporting point is arranged within a lower-side unit regionpartitioned by adjacent 4 lower-side supporting points.
 17. Theinspection apparatus for circuit board according to claim 16, whereinclearances between upper-side supporting points adjacent to each otherrelated to the upper-side unit region, and between lower-side supportingpoints adjacent to each other related to the lower-side unit region areeach 10 to 100 mm.
 18. The inspection apparatus for circuit boardaccording to claim 11, wherein the upper-side base plate and lower-sidebase plate are each composed of a glass fiber-reinforced epoxy resin andhave a thickness of 2 to 5 mm.
 19. An inspection process for circuitboard, which comprises: using the inspection apparatus for circuit boardaccording to claim 11, and in a measurable state that an inspectionobject circuit board is compressed by the upper-side board-compressingmember and lower-side board-compressing member by pressing theupper-side base plate and the lower-side base plate by the upper-sidesupports and the lower-side supports, respectively, deforming a complexstack composed of the inspection object circuit board and the upper-sideboard-compressing member and lower-side board-compressing member forcompressing the inspection object circuit board by shifting in thethickness-wise direction together with the upper-side base plate andlower-side base plate, at positions, over the whole body, respectivelypressed by the upper-side supports and lower-side supports in accordancewith the upper-side supporting points and lower-side supporting points,so as to carry out measurement of electric resistance.